微生物的代谢与调控

微生物的代谢与调控 100422 龙海 2010/11/30 steel bolts, screws and studs GB/T3098.6-2000 scope of this project are: 1, 2, 3 aluminium sheet curtain wall of glass curtain wall and the Aluminum plastic Board curtain wall 4, and stone curtain wall 5, and curtain wall buried pieces 6, and light steel points type glass rain canopy, and aluminum Board rain canopy 7, and aluminum Venetian 8, and outdoor advertising (containing roofing and the State surface advertising) 9 to spring glass door 10, and concrete structure and curtain wall between of layer between, and around fire seal blocking 11, and anti-mine 12, and daughter wall top processing 13, and pan light ming, engineering of tie construction 14, and buildings of deformation sewing (settlement sewing, and expansion joints,) 15, and After the detailed design drawings issued a wall embedded part is inconsistent with the tenderer needs to increase fixed curtain wall structure 16, decorative surfaces and decorative surface and joints between parts of other buildings facing sealing process, required to support the outer decoration of a hole, hole, plugging holes and so on. This works more decorative items, in order to ensure that the decoration construction progress and quality, trying to avoid construction does not ... Processing. After installation is complete if you have damaged galvanized parts should 目录 摘要................................................................................................................................. 3 1( 微生物的代谢与调控概述 .......................................................................................... 3 2( 微生物的初级代谢..................................................................................................... 3 2.1 糖类代谢 ........................................................................................................ 3 2.1.1 糖的种类及其作用................................................................................ 3 2.1.2 糖酵解过程 .......................................................................................... 4 2.1.3 糖酵解的控制....................................................................................... 5 2.1.4 糖酵解的意义....................................................................................... 6 2.1.5 三羧酸循环(TCA)过程....................................................................... 6 2.1.6 三羧酸循环的生物学意义 ..................................................................... 7 2.1.7 葡萄糖和蔗糖的微生物合成.................................................................. 8 2.2 脂类的代谢..................................................................................................... 8 2.2.1 脂的定义及分类 ................................................................................... 8 2.2.2 脂肪的分解代谢 ................................................................................... 8 2.2.3 脂肪酸的合成....................................................................................... 9 2.3 氨基酸的代谢 ................................................................................................. 9 2.3.1 氨基酸的分解代谢................................................................................ 9 2.3.2 氨基酸的合成代谢................................................................................ 9 2.4 核酸的代谢................................................................................................... 10 2.4.1 核酸的酶促降解过程及核苷酸的分解代谢........................................... 10 2.4.2 核苷酸的合成代谢.............................................................................. 10 3( 微生物的产能代谢................................................................................................... 10 3.1 能量的载体ATP ............................................................................................ 10 3.2 能量转化的途径............................................................................................ 10 4( 微生物的次级代谢................................................................................................... 11 4.1 次级代谢的类型............................................................................................ 11 4.2 次级代谢产物的生物合成.............................................................................. 11 4.3 次级代谢的特点............................................................................................ 11 4.4 次级代谢的生理功能..................................................................................... 11 5( 微生物代谢的调控................................................................................................... 12 5.1 酶活性调节................................................................................................... 12 5.2 酶含量的调节 ............................................................................................... 13 5.2.1酶合成的诱导和阻遏 ................................................................................ 13 5.2.2酶降解的调节........................................................................................... 13 6. 结束语 ..................................................................................................................... 13 steel bolts, screws and studs GB/T3098.6-2000 scope of this project are: 1, 2, 3 aluminium sheet curtain wall of glass curtain wall and the Aluminum plastic Board curtain wall 4, and stone curtain wall 5, and curtain wall buried pieces 6, and light steel points type glass rain canopy, and aluminum Board rain canopy 7, and aluminum Venetian 8, and outdoor advertising (containing roofing and the State surface advertising) 9 to spring glass door 10, and concrete structure and curtain wall between of layer between, and around fire seal blocking 11, and anti-mine 12, and daughter wall top processing 13, and pan light ming, engineering of tie construction 14, and buildings of deformation sewing (settlement sewing, and expansion joints,) 15, and After the detailed design drawings issued a wall embedded part is inconsistent with the tenderer needs to increase fixed curtain wall structure 16, decorative surfaces and decorative surface and joints between parts of other buildings facing sealing process, required to support the outer decoration of a hole, hole, plugging holes and so on. This works more decorative items, in order to ensure that the decoration construction progress and quality, trying to avoid construction does not ... Processing. After installation is complete if you have damaged galvanized parts should 微生物的代谢与调控 微生物的代谢与调控 摘要:本文以微生物的代谢为线索，对微生物的物质代谢、能量代谢以及微 生物代谢的调控途径进行了论述。重点阐述了微生物初级代谢中糖类、脂类、氨基酸和核酸四大类物质的代谢过程以及微生物的酶活性和酶含量两种代谢的调控途径。 关键词:物质代谢 能量代谢 酶活性调控 酶含量调控 1( 微生物的代谢与调控概述 新陈代谢是微生物生命活动的基本特征之一，是微生物生理学的核心，它包括微生物体内所进行的全部化学反应的总和，这些化学反应是由酶催化完成的。微生物的代谢包括分解代谢和合成代谢:微生物不断从周围环境中摄取营养物质，通过一系列的分解代谢，将复杂 通过一系列的合成代谢，将一些的有机物分解成简单的物质并释放能量，于此同时微生物又 简单的物质在消耗能量的条件下转变成自身的组织成分。分解代谢和合成代谢偶联于微生物体内，虽然对微生物起着不同的作用，但是两者都是将物质作为能量的载体，伴随着物质的代谢而实现能量的代谢。 微生物有的物质代谢过程具有明确的生理功能，对维持生命活动不可或缺，称为初级代谢，其代谢产物有氨基酸，核苷酸，糖，脂肪酸等;有的物质代谢过程没有明确的生理功能，并不是维持生命活动所必须称为次级代谢，其代谢产物有色素、抗生素，毒素，激素等。 尽管微生物代谢过程十分错综复杂，但通过其体内高效而灵敏的的调控系统在分子水平、细胞水平和个体水平，三个不同水平多层次的严格地调控下各种代谢过程进行的有条不紊，代谢产物既能满足微生物生命活动所必需，又不造成浪费。 2( 微生物的初级代谢 2.1 糖类代谢 2.1.1 糖的种类及其作用 微生物体内的糖按水解情况分类可分为单糖、双糖和多糖。糖类之于微生物的生物 学作用是多方面的:1.是微生物的结构成分;2.是微生物体内的主要能源物质;3.是其 他诸如氨基酸、核苷酸、脂等生物分子的合成前体;4.是细胞识别的信息分子。因此糖 steel bolts, screws and studs GB/T3098.6-2000 scope of this project are: 1, 2, 3 aluminium sheet curtain wall of glass curtain 3 wall and the Aluminum plastic Board curtain wall 4, and stone curtain wall 5, and curtain wall buried pieces 6, and light steel points type glass rain canopy, and aluminum Board rain canopy 7, and aluminum Venetian 8, and outdoor advertising (containing roofing and the State surface advertising) 9 to spring glass door 10, and concrete structure and curtain wall between of layer between, and around fire seal blocking 11, and anti-mine 12, and daughter wall top processing 13, and pan light ming, engineering of tie construction 14, and buildings of deformation sewing (settlement sewing, and expansion joints,) 15, and After the detailed design drawings issued a wall embedded part is inconsistent with the tenderer needs to increase fixed curtain wall structure 16, decorative surfaces and decorative surface and joints between parts of other buildings facing sealing process, required to support the outer decoration of a hole, hole, plugging holes and so on. This works more decorative items, in order to ensure that the decoration construction progress and quality, trying to avoid construction does not ... Processing. After installation is complete if you have damaged galvanized parts should 类是微生物体内非常重要的一类有机化合物。 2.1.2 糖酵解过程 双糖和多糖可通过酶促降解反应，降解为葡萄糖、果糖等较为简单的有机碳化合物，然后进行氧化分解。各种氧化分解的过程不尽相同，这里以葡萄糖的糖酵解过程和三羧酸循环过程为例对糖类分解代谢进行阐述。 糖酵解是酶将葡萄糖降解为丙酮酸并伴随ATP生成的过程。是一切有机体中普遍存在的葡萄糖降解途径。该过程在微生物的细胞质内进行，可分为4个阶段，10个步骤:第一阶段为葡萄糖转化为1,6-二磷酸果糖的过程，该阶段包含3个步骤(见图一)。虽然葡萄糖的氧化反应是放能反应，但葡萄糖是较稳定的化合物，要使之放能就必须 2+使葡萄糖由稳定态变为活化态，故葡萄糖首先在Mg参与的条件下，通过己糖磷酸激酶的催化，作用消耗1分子ATP磷酸化成6-磷酸葡萄糖(步骤?)。6-磷酸葡萄糖通过磷酸己糖异构酶的催化作用实现结构异构，生成6-磷酸果糖(步骤 2+?)。6-磷酸果糖在Mg的参与并消耗1分子ATP的条件下通过磷酸果糖激酶的作用生成1.6-二磷酸果糖(步骤?)。该过程中包含的反应均不可逆。 图一 糖酵解第一阶段 第二阶段为1.6-二磷酸果糖转化为3-磷酸甘油醛的过程，该阶段包含两个步骤(见图二)。1.6-二磷酸果糖先在醛缩酶的作用下生成磷酸二羟丙酮(步骤?)，再通过磷酸丙糖异构酶的作用使磷酸二羟丙酮的基团换位生成3-磷酸甘油醛(步骤?)。该阶段的反应均可逆。 图二 糖酵解第二阶段 第三阶段为3-磷酸甘油醛转化为2-磷酸甘油酸的过程，该阶段包含三个步骤(见图三)。3-磷酸甘油醛首先在磷酸参与反应的条件下，通过3-磷酸甘油醛脱氢酶的催化 ++作用氧化成1.3-二磷酸甘油酸并释放两个电子和一个H，电子和H传递给电子受体 ++NAD生成NADH+ H并将能量转移到高能磷酸键中(步骤?);1.3-二磷酸甘油酸并不 steel bolts, screws and studs GB/T3098.6-2000 scope of this project are: 1, 2, 3 aluminium sheet curtain wall of glass curtain wall and the Aluminum plastic Board curtain wall 4, and stone curtain wall 5, and curtain wall buried pieces 6, and light steel points type glass rain canopy, and aluminum Board rain canopy 7, and aluminum Venetian 8, and outdoor advertising (containing roofing and the State surface advertising) 9 to spring glass door 10, and concrete structure and curtain wall between of layer between, and around fire seal blocking 11, and anti-mine 12, and daughter wall top processing 13, and pan light ming, engineering of tie construction 14, and buildings of deformation sewing (settlement sewing, and expansion joints,) 15, and After the detailed design drawings issued a wall embedded part is inconsistent with the tenderer needs to increase fixed curtain wall structure 16, decorative surfaces and decorative surface and joints between parts of other buildings facing sealing process, required to support the outer decoration of a hole, hole, plugging holes and so on. This works more decorative items, in order to ensure that the decoration construction progress and quality, trying to avoid construction does not ... Processing. After installation is complete if you have damaged galvanized parts should 微生物的代谢与调控 稳定，它会在在磷酸甘油酸激酶的作用下失去高能磷酸键，生成3-磷酸甘油酸，并偶联生成1分子ATP(步骤?)。该步骤是糖酵解过程中第一次发生底物水平磷酸化;3-磷酸甘油酸再通过磷酸甘油酸变位酶的作用转成2-磷酸甘油酸(步骤?)。该阶段的反应均可逆，通过该阶段的反应，1分子葡萄糖可以生成2分子的ATP。 图三 糖酵解第三阶段 第四阶段为2-磷酸甘油酸转化为丙酮酸的过程，该阶段包含两个步骤(见图四)。2-磷酸甘油酸通过烯醇化酶的作用脱去一分子水生成磷酸烯醇式丙酮酸(步骤?);磷酸烯醇式丙酮酸在丙酮酸激酶的催化下生成烯醇式丙酮酸，并伴随该过程生成1分子的ATP(步骤?)。该步骤是糖酵解过程中发生的第二次底物水平的磷酸化。烯醇式丙酮酸并不稳定，会自动转变成丙酮酸。通过该阶段的反应，1分子葡萄糖可生成2分子的ATP。 图四 糖酵解第四阶段 以上四个阶段即为葡萄糖糖酵解的全过程。在糖酵解整个过程中，葡萄糖先通过一、二两个阶段由一个六碳化合物转化为两个三碳化合物，消耗2分子ATP用于葡萄糖的活化。而每1分子三碳化合物通过三、四两个阶段，发生一次氧化反应生成1分子NADH，发生两次底物水平磷酸化，生成2分子ATP，得到最终产物1分子丙酮酸。因此葡萄糖的糖酵解过程净生成2分子ATP，2分子NADH和2分子丙酮酸。 2.1.3 糖酵解的控制 微生物对酵解速度调控的目的是为了满足微生物对能量及碳骨架的需求。其调控糖酵解速度的方式是多样的，但经过研究发现，在代谢途径中，催化不可逆反应的酶所处的部位是控制代谢反应的有力部位。从上述糖酵解的四个阶段可以看出，己糖激酶、磷酸果糖激酶、丙酮酸激酶催化的是三步不可逆反应，微生物可通过这三种酶实现对糖酵解速度的调控。 steel bolts, screws and studs GB/T3098.6-2000 scope of this project are: 1, 2, 3 aluminium sheet curtain wall of glass curtain 5 wall and the Aluminum plastic Board curtain wall 4, and stone curtain wall 5, and curtain wall buried pieces 6, and light steel points type glass rain canopy, and aluminum Board rain canopy 7, and aluminum Venetian 8, and outdoor advertising (containing roofing and the State surface advertising) 9 to spring glass door 10, and concrete structure and curtain wall between of layer between, and around fire seal blocking 11, and anti-mine 12, and daughter wall top processing 13, and pan light ming, engineering of tie construction 14, and buildings of deformation sewing (settlement sewing, and expansion joints,) 15, and After the detailed design drawings issued a wall embedded part is inconsistent with the tenderer needs to increase fixed curtain wall structure 16, decorative surfaces and decorative surface and joints between parts of other buildings facing sealing process, required to support the outer decoration of a hole, hole, plugging holes and so on. This works more decorative items, in order to ensure that the decoration construction progress and quality, trying to avoid construction does not ... Processing. After installation is complete if you have damaged galvanized parts should 2.1.4 糖酵解的意义 糖酵解对微生物主要有三方面的意义:一方面，糖酵解是葡萄糖在微生物体内进行 有氧或无氧分解的共同途径，通过糖酵解，微生物体获得生命活动所需要的能量;另一 方面，糖酵解途径的许多中间产物可为氨基酸、脂类合成提供碳骨架;第三方面，糖酵 解可为糖异生提供基本途径。 2.1.5 三羧酸循环(TCA)过程 经糖酵解产生的丙酮酸，在有氧的条件下会以乙酰CoA的形式进入三羧酸循环(见 图五)，最终生成水和CO，并释放能量。 2 图五 三羧酸循环(TCA) 丙酮酸进入线粒体后首先在丙酮酸脱氢酶复合体的催化作用下分五步反应生成乙酰 CoA，自此进入TCA。可见该步骤是连接糖酵解和TCA的纽带。丙酮酸生成乙酰CoA的过steel bolts, screws and studs GB/T3098.6-2000 scope of this project are: 1, 2, 3 aluminium sheet curtain wall of glass curtain wall and the Aluminum plastic Board curtain wall 4, and stone curtain wall 5, and curtain wall buried pieces 6, and light steel points type glass rain canopy, and aluminum Board rain canopy 7, and aluminum Venetian 8, and outdoor advertising (containing roofing and the State surface advertising) 9 to spring glass door 10, and concrete structure and curtain wall between of layer between, and around fire seal blocking 11, and anti-mine 12, and daughter wall top processing 13, and pan light ming, engineering of tie construction 14, and buildings of deformation sewing (settlement sewing, and expansion joints,) 15, and After the detailed design drawings issued a wall embedded part is inconsistent with the tenderer needs to increase fixed curtain wall structure 16, decorative surfaces and decorative surface and joints between parts of other buildings facing sealing process, required to support the outer decoration of a hole, hole, plugging holes and so on. This works more decorative items, in order to ensure that the decoration construction progress and quality, trying to avoid construction does not ... Processing. After installation is complete if you have damaged galvanized parts should 微生物的代谢与调控 程通过可逆磷酸化调节和产物调节得到严格的调控。 三羧酸循环的过程可分为8个步骤: 1) 乙酰CoA与草酰乙酸缩合形成柠檬酸，该过程由柠檬酸合酶催化。柠檬酸合酶的组氨 +酸残基作为碱基首先与乙酰CoA作用，使乙酰CoA的甲基上失去一个H，生成的碳 阴离子对草酰乙酸的羰基碳进行攻击，生成柠檬酰CoA中间体，然后高能硫酯键水 解放出游离的柠檬酸，使反应不可逆地向右进行。该步骤是TCA的一个重要调控步 骤，柠檬酸合酶是调控酶。其中ATP、α-酮戊二酸等物质可抑制柠檬酸合酶的活性而 阻碍TCA的进行，而AMP可激活柠檬酸合酶的活性来推动TCA。 2) 不易氧化的柠檬酸在顺乌头酸酶的催化作用下异构成易于氧化的异柠檬酸。 3) 异柠檬酸通过异柠檬酸脱氢酶的催化作用氧化脱羧生成α-酮戊二酸。该步骤是TCA 中第一次氧化脱羧，反应过程不可逆，是TCA的另一个调控步骤，其中异柠檬酸脱 氢酶是调控酶。 4) α-酮戊二酸通过α-酮戊二酸脱氢酶复合体的催化作用氧化脱羧成为琥珀酰CoA，这 是TCA中的第二次氧化脱羧，该步骤中α-酮戊二酸脱氢酶作为一个调控酶可以对 TCA进行调控。 5) 在琥珀酰CoA合成酶的作用下，琥珀酰CoA的硫酯键水解，生成琥珀酸和CoA并释 放能量。该步骤释放的自由能用于合成三磷酸鸟苷(GTP)，最终生成ATP。这是TCA 中唯一底物水平磷酸化直接产生高能磷酸化合物的步骤。 6) 琥珀酸在琥珀酸脱氢酶的作用下，通过第三次氧化脱氢反应生成延胡索酸。丙二酸是 琥珀酸的类似物，它是该步骤催化酶琥珀酸脱氢酶强有力的竞争性抑制物，通过其抑 制作用，甚至可以阻断TCA。 7) 延胡索酸酶通过对延胡索酸的反式双键作用，使其水化生成苹果酸。 8) 苹果酸在苹果酸脱氢酶的作用下，通过TCA的第四次氧化反应生成草酰乙酸。 TCA每轮循环都有2个C原子以乙酰CoA形式进入，再通过两步脱羧反应，有两个C原子以CO的形式离开。整个循环需消耗2分子HO，生成12.5分子的ATP，虽然反22 应过程不消耗氧，但是离开氧整个循环无法运行。 2.1.6 三羧酸循环的生物学意义 三羧酸循环的生物学意义主要现在两方面:一方面它与糖酵解构成糖的有氧代谢途径，是机体利用糖氧化获得能量的最有效的方式。通过能量计算可得，1分子葡萄糖 steel bolts, screws and studs GB/T3098.6-2000 scope of this project are: 1, 2, 3 aluminium sheet curtain wall of glass curtain 7 wall and the Aluminum plastic Board curtain wall 4, and stone curtain wall 5, and curtain wall buried pieces 6, and light steel points type glass rain canopy, and aluminum Board rain canopy 7, and aluminum Venetian 8, and outdoor advertising (containing roofing and the State surface advertising) 9 to spring glass door 10, and concrete structure and curtain wall between of layer between, and around fire seal blocking 11, and anti-mine 12, and daughter wall top processing 13, and pan light ming, engineering of tie construction 14, and buildings of deformation sewing (settlement sewing, and expansion joints,) 15, and After the detailed design drawings issued a wall embedded part is inconsistent with the tenderer needs to increase fixed curtain wall structure 16, decorative surfaces and decorative surface and joints between parts of other buildings facing sealing process, required to support the outer decoration of a hole, hole, plugging holes and so on. This works more decorative items, in order to ensure that the decoration construction progress and quality, trying to avoid construction does not ... Processing. After installation is complete if you have damaged galvanized parts should 通过糖酵解和三羧酸循环后可生成30或32个分子的ATP，可以为机体提供大量的能量;另一方面它是糖、脂类、蛋白质代谢联络的枢纽，其中间产物在许多生物合成中作前体。 2.1.7 葡萄糖和蔗糖的微生物合成 葡萄糖主要通过微生物体内的糖异生过程合成。所谓糖异生就是丙酮酸、乳酸、氨基酸、甘油等非糖类物质转变成葡萄糖的过程，该过程在线粒体或细胞液中进行。其反应途径除了糖酵解中三步不可逆的反应外大部分与糖酵解的逆反应相同。 葡萄糖被吸收后，在消耗ATP的情况下，使之磷酸化，生成6-磷酸葡萄糖。再经异构催化，转变为1-磷酸葡萄糖。该糖的磷酸酯在参与生物合成或相互转化之前，必须变成激活状态，即变成糖核苷酸。糖核苷酸是单糖与核苷二磷酸结合生成的衍生物，主要包括糖核苷二磷酸，它是微生物合成双糖和多糖的糖基供体。微生物体内蔗糖的合成就是1-磷酸葡萄糖先转化成糖核苷二磷酸，再通过酶的作用与果糖结合生成蔗糖。 2.2 脂类的代谢 2.2.1 脂的定义及分类 脂是一类结构多样，低溶于水而高溶于非极性溶剂的生物有机分子，可作为很多微生物生长的碳源和能源。脂类按化学组成进行分类，可被分为单纯脂类、复合脂类和衍生脂类。单纯脂类是指由脂肪酸和醇类所形成的酯，如甘油三酯(即脂肪)等，复合脂类是指除了含有脂肪酸和醇之外，还含有其它成分的脂类，如磷脂、糖脂等。衍生脂类则大部分不包含脂肪酸。 2.2.2 脂肪的分解代谢 脂肪首先通过脂肪酶、甘油二酯脂肪酶和甘油单酯脂肪酶的催化作用水解成甘油和脂肪酸。接着甘油和脂肪酸再进行各自的氧化分解。 甘油在甘油激酶的作用下生成3-磷酸甘油，再通过磷酸甘油脱氢酶的催化作用生成磷酸二羟丙酮，并由此进入糖酵解途径或糖异生途径。从该过程可以看出，磷酸二羟丙酮是糖代谢和脂代谢相联系的一座桥梁。 脂肪酸的氧化分解过程是一个逐步脱羧和碳链降解过程，该过程由一系列的酶催化， ，并需要CoA、NAD等参与。饱和脂肪酸的β-氧化过程为脂肪酸首先在脂酰CoA合成酶的催化下，消耗2分子高能磷酸键生成脂酰CoA，该过程也被称作脂肪酸的活化过程。生成的脂酰CoA经转运进入线粒体，再通过脱氢、加水、再脱氢和硫解过程生成乙酰 steel bolts, screws and studs GB/T3098.6-2000 scope of this project are: 1, 2, 3 aluminium sheet curtain wall of glass curtain wall and the Aluminum plastic Board curtain wall 4, and stone curtain wall 5, and curtain wall buried pieces 6, and light steel points type glass rain canopy, and aluminum Board rain canopy 7, and aluminum Venetian 8, and outdoor advertising (containing roofing and the State surface advertising) 9 to spring glass door 10, and concrete structure and curtain wall between of layer between, and around fire seal blocking 11, and anti-mine 12, and daughter wall top processing 13, and pan light ming, engineering of tie construction 14, and buildings of deformation sewing (settlement sewing, and expansion joints,) 15, and After the detailed design drawings issued a wall embedded part is inconsistent with the tenderer needs to increase fixed curtain wall structure 16, decorative surfaces and decorative surface and joints between parts of other buildings facing sealing process, required to support the outer decoration of a hole, hole, plugging holes and so on. This works more decorative items, in order to ensure that the decoration construction progress and quality, trying to avoid construction does not ... Processing. After installation is complete if you have damaged galvanized parts should 微生物的代谢与调控 CoA和缩短了两个碳原子的脂酰CoA，其中乙酰CoA进入TCA，脂酰CoA则进入下一轮 循环。以16C软脂酸为例，进行饱和脂肪酸的β-氧化过程的能量计算。16C软脂酸经 过7次循环，产生7个NADH，7个FADH， 8分子乙酰CoA。7个NADH，7个FADH22 经过呼吸链分别产生17.5和10.5分子的ATP，而8分子的乙酰CoA进入TCA后可生成 80分子的ATP，活化过程需消耗2分子ATP，因此软脂酸的β-氧化过程可净产生106 分子的ATP。不饱各脂肪酸的氧化途径与饱和脂肪酸的氧化途径基本上是一样的，只是 某些步骤中还需其他的酶参与。 2.2.3 脂肪酸的合成 奇数碳和偶数碳的引物不同，这里以软脂酸为例说明脂肪酸的合成过程。软脂酸的合成是以乙酰CoA作为起始引物，乙酰CoA通过柠檬酸穿梭过程将其从线粒体内运转至胞液。在乙酰CoA羧化酶的作用下，消耗ATP生成丙二酸单酰CoA，丙二酸单酰CoA是合成脂肪酸链的材料。软脂酸的合成是通过六种酶的催化完成的，这六种酶通过硫酯键固定在脂酰基载体蛋白(ACP)上。乙酰CoA和丙二酸单酰CoA为原料，通过六种酶的催化作用依次 脱水反应、再还原发生乙酰基转移反应、丙二酸单酰基转移反应、缩合反应、还原反应、 反应生成丁酰-ACP，丁酰-ACP与丙二酸单酰-ACP结合，再重复缩合、还原、脱水、再还原的过程，直至生成软脂酰-ACP，软脂酰-ACP通过硫酯酶的催化作用水解后便得到软脂酸。 2.3 氨基酸的代谢 2.3.1 氨基酸的分解代谢 微生物分解氨基酸有三种方式:脱羧、脱氨和转氨。目的是使脱羧或脱氨后的有机 酸，转变成丙酮酸，乙酰CoA或TCA循环的中间体，最后在TCA循环被氧化放出能量; 有些有机酸也能作为合成细胞成分的碳源。 2.3.2 氨基酸的合成代谢 氨基酸中的氮来源于无机氮，无机氮通过微生物的固氮作用及氨化作用转化为NH，3 再通过氨的同化将NH转化为有机氮。氨同化的途径有多种，细菌可在谷氨酸脱氢酶的3 作用下将NH同化为谷氨酸，谷氨酸作为氨基供体，通过转氨基作用参与其它氨基酸的3 合成。 氨基酸的合成需要碳架，而这些碳架往往来源于糖酵解、TCA和磷酸戊糖途径的中 间体，氨基酸的代谢通过这种方式可以和糖类代谢联系起来。根据氨基酸的前体可将氨 基酸的合成分为5大类:丙氨酸族氨基酸的合成、丝氨酸族氨基酸的合成、天冬氨酸族 steel bolts, screws and studs GB/T3098.6-2000 scope of this project are: 1, 2, 3 aluminium sheet curtain wall of glass curtain 9 wall and the Aluminum plastic Board curtain wall 4, and stone curtain wall 5, and curtain wall buried pieces 6, and light steel points type glass rain canopy, and aluminum Board rain canopy 7, and aluminum Venetian 8, and outdoor advertising (containing roofing and the State surface advertising) 9 to spring glass door 10, and concrete structure and curtain wall between of layer between, and around fire seal blocking 11, and anti-mine 12, and daughter wall top processing 13, and pan light ming, engineering of tie construction 14, and buildings of deformation sewing (settlement sewing, and expansion joints,) 15, and After the detailed design drawings issued a wall embedded part is inconsistent with the tenderer needs to increase fixed curtain wall structure 16, decorative surfaces and decorative surface and joints between parts of other buildings facing sealing process, required to support the outer decoration of a hole, hole, plugging holes and so on. This works more decorative items, in order to ensure that the decoration construction progress and quality, trying to avoid construction does not ... Processing. After installation is complete if you have damaged galvanized parts should 氨基酸的合成、谷氨酸族氨基酸的合成和组氨酸族和芳香族氨基酸的合成。这5类合成分别以不同的前体为基础，在各种酶的催化作用下通过转氨基等作用生成不同的氨基酸。 2.4 核酸的代谢 2.4.1 核酸的酶促降解过程及核苷酸的分解代谢 核酸首先通过核酸酶的作用分解为核苷酸，核苷酸再通过核苷酸酶的催化作用降解为磷酸和核苷，最终核苷在核苷磷酸化酶的作用下分解成磷酸-戊糖和碱基，磷酸-戊糖进入磷酸戊糖途径或重新合成核酸。碱基中的嘌呤首先在脱氨酶的作用下水解脱去氨基，再将其分解成NH、CO及有机酸;碱基中的嘧啶如果有氨基先脱氨基，接着嘧啶32 环在相应的水解酶催化下解开，然后逐个的水解各个骨架原子最终释放出CO、NH，23并生成相应的酸。 2.4.2 核苷酸的合成代谢 核苷酸的合成的基本途径包括“从头合成”途径和补救合成途径。所谓“从头合成”途径是指利用磷酸核糖、氨基酸及CO等简单物质为原料，经一系列酶促反应，合成嘌2 呤核苷酸的途径;补救合成途径是指利用体内游离的嘌呤核苷或嘧啶核苷，经过简单的反应过程，合成核苷酸的途径。嘧啶核苷酸的合成过程与嘌呤核苷酸的合成过程有所不同，它首先合成嘧啶环，再与磷酸核糖结合，生成尿嘧啶核苷酸，最后由尿嘧啶核苷酸转化为胞嘧啶核苷酸和胸腺嘧啶脱氧核苷酸。 3( 微生物的产能代谢 3.1 能量的载体ATP 微生物通过分解代谢或光合作用产生的能量除了用于运动、物质运输、发光发热外，最常见的是将能量转移到高能化合物中，以化学键能形式储存起来。ATP是微生物体内一种重要的高能化合物，它作为能量的载体，将微生物通过分解代谢或光合作用产生的能量经过能量转化后储存起来，用于物质的合成。 3.2 能量转化的途径 微生物通过分解代谢和光合作用产生的能量需进行转化后储存于ATP中，实现这种转化的途径有3种: 1) 底物水平磷酸化 steel bolts, screws and studs GB/T3098.6-2000 scope of this project are: 1, 2, 3 aluminium sheet curtain wall of glass curtain wall and the Aluminum plastic Board curtain wall 4, and stone curtain wall 5, and curtain wall buried pieces 6, and light steel points type glass rain canopy, and aluminum Board rain canopy 7, and aluminum Venetian 8, and outdoor advertising (containing roofing and the State surface advertising) 9 to spring glass door 10, and concrete structure and curtain wall between of layer between, and around fire seal blocking 11, and anti-mine 12, and daughter wall top processing 13, and pan light ming, engineering of tie construction 14, and buildings of deformation sewing (settlement sewing, and expansion joints,) 15, and After the detailed design drawings issued a wall embedded part is inconsistent with the tenderer needs to increase fixed curtain wall structure 16, decorative surfaces and decorative surface and joints between parts of other buildings facing sealing process, required to support the outer decoration of a hole, hole, plugging holes and so on. This works more decorative items, in order to ensure that the decoration construction progress and quality, trying to avoid construction does not ... Processing. After installation is complete if you have damaged galvanized parts should 微生物的代谢与调控 微生物在生物氧化过程中底物生成含高能键化合物，高能键通过相应酶的作用可以 直接偶联ATP的合成。这种能量转化方式主要存在于发酵作用中，其特点是底物在氧 化过程中脱下的电子或氢无需经过电子传递链传递，而是通过酶促反应直接交给底物 本事氧化的产物，同时将反应过程中释放的能量交给ADP，合成ATP。 2) 氧化磷酸化 底物在氧化过程中生成的NADH和FADH可以通过位于线粒体内膜上的电子传递链2 将传递给氧或其他氧化型物质，在这一过程中偶联ATP的合成，这种能量转化方式主 要存在于有氧呼吸和无氧呼吸作用中。 3) 光合磷酸化 光合磷酸化是指光能转化为化学能的过程，产氧型光合作用偶那个过非环式光合磷 酸化合成ATP，不产氧型光合作用通过环式光合磷酸化合成ATP。 4( 微生物的次级代谢 4.1 次级代谢的类型 相比于初级代谢，次级代谢没有明确的生理功能，也并非维持微生物生命活动所必须，其划分种类的方式也多样。根据产物合成途径可以分为四种类型:与糖代谢有关的类型、与脂肪酸代谢有关的类型、与萜烯和甾体化合物有关的类型、与TCA环有关的类型;根据产物作用可以区分为抗生素、激素、生物碱、毒素及维生素。 4.2 次级代谢产物的生物合成 次级代谢以初级代谢产物为前体，通过前体聚合、结构修饰和不同组分的装配三个步骤合成次级代谢产物。 4.3 次级代谢的特点 次级代谢与初级代谢相比，有其独有的特点: 1)次级代谢以初级代谢产物为前体，并受初级代谢的调节; 2)次级代谢产物一般在菌体生长后期合成; 3)次级代谢酶的专一性低; 4)次级代谢产物的合成具有菌株特异性; 5)次级代谢可能与质粒有关。 4.4 次级代谢的生理功能 次级代谢的生理功能主要体现在四个方面:1.维持初级代谢的平衡。因为次级代谢产物 steel bolts, screws and studs GB/T3098.6-2000 scope of this project are: 1, 2, 3 aluminium sheet curtain wall of glass curtain 11 wall and the Aluminum plastic Board curtain wall 4, and stone curtain wall 5, and curtain wall buried pieces 6, and light steel points type glass rain canopy, and aluminum Board rain canopy 7, and aluminum Venetian 8, and outdoor advertising (containing roofing and the State surface advertising) 9 to spring glass door 10, and concrete structure and curtain wall between of layer between, and around fire seal blocking 11, and anti-mine 12, and daughter wall top processing 13, and pan light ming, engineering of tie construction 14, and buildings of deformation sewing (settlement sewing, and expansion joints,) 15, and After the detailed design drawings issued a wall embedded part is inconsistent with the tenderer needs to increase fixed curtain wall structure 16, decorative surfaces and decorative surface and joints between parts of other buildings facing sealing process, required to support the outer decoration of a hole, hole, plugging holes and so on. This works more decorative items, in order to ensure that the decoration construction progress and quality, trying to avoid construction does not ... Processing. After installation is complete if you have damaged galvanized parts should 是以初级代谢产物为前体，而次级代谢产物一般在菌体生长后期合成，此时酶活性下降，初级代谢产物过剩，次级代谢将累积的初级代谢产物进行其他形式的转化，以维持初级代谢的平衡;2.次级代谢产物是贮藏物质的一种形式;3.使菌体在生存竞争中占优势。如有的菌种产生抗生素，抑制其他微生物的生长，对自身的生长却没有影响;4.与细胞分化有关。有研究指出抗生素是细胞分化的重要物质，除此之外有人从霉菌中分离出了诱导细胞分化的调节因子，该因子在微生物生长阶段无任何功能，可被认为是次级代谢产物。 5( 微生物代谢的调控 微生物具有高度严密的自我调控系统，微生物通过代谢调控，可以实现营养物质最经济的利用，合成出既能满足自身生长、繁殖所需，又不过剩的代谢产物。微生物的代谢调控都是通过协调控制酶来实现的，包括控制酶的活性、控制酶的含量等手段。 5.1 酶活性调节 酶活性的调节就是通过控制酶分子的活性的方式来控制代谢的速率，其特点是反应速度快。酶活性调节的机制有多种，归纳起来如下: 1) 变构效应 通过变构方式实现酶活性调节的酶主要是变构酶，变构酶的调节部位在与调节物结合的变构部位，该部位通过与正、负调节物的结合实现酶活性的条件。 2) 共价修饰与级联放大系统 共价修饰是通过在共价修饰酶的酶蛋白某些氨基酸残基上增、减基团的办法，使酶在活性态与非活性态间的相互转化，从而实现对酶活性的调节的方式。 级联放大系统是指连锁代谢反应中一个酶被激活后，连续地发生其它酶被激活，导致原始信号放大的酶链反应系统。 酶的共价修饰反应是酶促反应，也就是一个连锁代谢反应。因此，只要有少量信号分子(如激素)存在，即可通过级联放大系统加速这种酶促反应，而使大量的另一种酶发生化学修饰，从而获得放大效应。 3) 酶原激活 将本来没有活性的酶原通过切断某些肽键或切掉某些肽段来改变酶原的空间构象，使其有活性。 4) 酶分子聚合与解聚 一些酶的活性可以通过酶分子亚基间的聚合与解聚实现调节，如:谷氨酸脱氢酶。 steel bolts, screws and studs GB/T3098.6-2000 scope of this project are: 1, 2, 3 aluminium sheet curtain wall of glass curtain wall and the Aluminum plastic Board curtain wall 4, and stone curtain wall 5, and curtain wall buried pieces 6, and light steel points type glass rain canopy, and aluminum Board rain canopy 7, and aluminum Venetian 8, and outdoor advertising (containing roofing and the State surface advertising) 9 to spring glass door 10, and concrete structure and curtain wall between of layer between, and around fire seal blocking 11, and anti-mine 12, and daughter wall top processing 13, and pan light ming, engineering of tie construction 14, and buildings of deformation sewing (settlement sewing, and expansion joints,) 15, and After the detailed design drawings issued a wall embedded part is inconsistent with the tenderer needs to increase fixed curtain wall structure 16, decorative surfaces and decorative surface and joints between parts of other buildings facing sealing process, required to support the outer decoration of a hole, hole, plugging holes and so on. This works more decorative items, in order to ensure that the decoration construction progress and quality, trying to avoid construction does not ... Processing. After installation is complete if you have damaged galvanized parts should 微生物的代谢与调控 5) 抑制剂或激活剂 5.2 酶含量的调节 酶含量的调节包括酶合成的调节和酶降解的调节，二者都是通过控制酶的含量来调节代谢速率。该调节是处于基因表达水平的一种调节。 5.2.1酶合成的诱导和阻遏 根据酶与底物的关系可将酶分为固有酶和诱导酶，若酶与底物存在无关，则称其为固有酶，而如果依赖于底物或底物类似物而产生的酶就是诱导酶。诱导酶是通过诱导物的诱导作用而产生，它充分体现了微生物代谢调控的经济性原则。 某些代谢物可以通过阻止编码某种或某些酶的基因的表达，来阻止某种酶或某些酶的合成，这种现象叫酶合成的阻遏作用，被阻止合成的酶叫阻遏酶。酶合成的阻遏分为终产物反馈阻遏和分解代谢阻遏两种类型，主要是依据引发阻遏作用的代谢物的类型划分的。 5.2.2酶降解的调节 许多代谢关键酶和受到严格调控的酶都会在蛋白水解酶的催化作用下迅速降解，使酶的含量下降，进而降低与这些酶相关代谢的代谢速率。 6. 结束语 通过对微生物代谢与调控的研究可以很好的理解微生物生命活动中诸多现象和规律的本质，但是到目前为止，无论是代谢过程的研究，还是调节机制研究，还有很多内容尚不透彻，需作进一步的深入研究。 steel bolts, screws and studs GB/T3098.6-2000 scope of this project are: 1, 2, 3 aluminium sheet curtain wall of glass curtain 13 wall and the Aluminum plastic Board curtain wall 4, and stone curtain wall 5, and curtain wall buried pieces 6, and light steel points type glass rain canopy, and aluminum Board rain canopy 7, and aluminum Venetian 8, and outdoor advertising (containing roofing and the State surface advertising) 9 to spring glass door 10, and concrete structure and curtain wall between of layer between, and around fire seal blocking 11, and anti-mine 12, and daughter wall top processing 13, and pan light ming, engineering of tie construction 14, and buildings of deformation sewing (settlement sewing, and expansion joints,) 15, and After the detailed design drawings issued a wall embedded part is inconsistent with the tenderer needs to increase fixed curtain wall structure 16, decorative surfaces and decorative surface and joints between parts of other buildings facing sealing process, required to support the outer decoration of a hole, hole, plugging holes and so on. This works more decorative items, in order to ensure that the decoration construction progress and quality, trying to avoid construction does not ... Processing. After installation is complete if you have damaged galvanized parts should