Cyclohexa‐1,5‐diene‐1‐carboxyl‐CoA hydratase, an enzyme involved in anaerobic metabolism of benzoyl‐CoA in the denitrifying bacterium Thauera aromatica
Cyclohexa‐1,5‐diene‐1‐carboxyl‐CoA hydratase, an enzyme involved in anaerobic metabolism of benzoyl‐CoA in the denitrifying bacterium Thauera aromatica
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环六-1,5-二烯-1-羧基辅酶A水合酶，一种参与反硝化细菌Thaueraaromatica中苯甲酰辅酶A厌氧代谢的酶
DOI：
10.1046/j.1432-1327.1998.2550618.x
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发表时间：
1998
期刊：
影响因子：
5.4
通讯作者：
G. Fuchs
中科院分区：
文献类型：
--
作者：
D. Laempe;W. Eisenreich;A. Bacher;G. Fuchs
许多芳香族化合物可以在缺氧条件下通过苯甲酰辅酶A作为共同中间体被细菌代谢。苯甲酰辅酶A代谢的中心途径是由ATP驱动的芳环还原产生环己-1，5-二烯-1-羧基辅酶A启动的。1，5-二烯酰-CoA中间体被认为通过特定的二烯酰-CoA水合酶催化水与双键之一的正式加成而转化为6-羟基环己-1-烯-1-羧基-CoA。
这种双烯酰辅酶A水合酶在苯甲酸盐厌氧生长后在发酵细菌Thauera aromatica中检测到。底物和产品进行了确认，并开发了一个方便的分光光度测定。底物和产物的平衡浓度几乎相等。与乙酸盐相反，苯甲酸盐在缺氧生长后诱导酶活性。 从T.发现其对环状1，5-二烯酰基-CoA具有高度特异性。第二个29 kDa的烯酰辅酶A水合酶作用于巴豆酰辅酶A;这种高活性的烯酰辅酶A水合酶也缓慢地作用于环己-1-烯-1-羧基辅酶A。双烯酰辅酶A水合酶活性的表达调控、动力学常数、底物特异性和细胞提取物中酶的比活性提供了证据，证明双烯酰辅酶A水合酶是T.芳香的
沼泽红球藻提取物具有较高的环己-1-烯-1-羧基-CoA水合酶活性，但不具有1，5-二烯酰-CoA水合酶活性。看来，苯甲酰辅酶A途径的变体在R.沼泽地，其中不发生1，5-二烯酰-CoA的水合作用。相反，环己-1-烯-1-羧基-CoA水合为2-羟基环己烷-1-羧基-CoA。
Many aromatic compounds can be metabolized by bacteria under anoxic conditions via benzoyl-CoA as the common intermediate. The central pathway of benzoyl-CoA metabolism is initiated by an ATP-driven reduction of the aromatic ring producing cyclohexa-1,5-diene-1-carboxyl-CoA. The 1,5-dienoyl-CoA intermediate is thought to be transformed to 6-hydroxycyclohex-1-ene-1-carboxyl-CoA by a specific dienoyl-CoA hydratase catalyzing the formal addition of water to one of the double bonds.
This dienoyl-CoA hydratase was detected in the denitrifying bacterium Thauera aromatica after anaerobic growth with benzoate. Substrate and product were confirmed and a convenient spectrophotometric assay was developed. The equilibrium concentrations of substrate and product were almost equal. Enzyme activity was induced after anoxic growth with benzoate, in contrast to acetate. The enzyme of 28 kDa was purified from T. aromatica and was found to be highly specific for the cyclic 1,5-dienoyl-CoA. A second 29-kDa enoyl-CoA hydratase acted on crotonyl-CoA; this highly active enoyl-CoA hydratase also acted slowly on cyclohex-1-ene-1-carboxyl-CoA. The regulation of expression of dienoyl-CoA hydratase activity, the kinetic constants, the substrate specificity, and the specific activity of the enzyme in cell extract provide evidence that dienoyl-CoA hydratase is the second enzyme of the central benzoyl-CoA pathway of anaerobic aromatic metabolism in T. aromatica.
Extracts of Rhodopseudomonas palustris contained high activity of cyclohex-1-ene-1-carboxyl-CoA hydratase, but no 1,5-dienoyl-CoA hydratase activity. It appears that a variant of the benzoyl-CoA pathway is operating in R. palustris in which hydration of the 1,5-dienoyl-CoA does not take place. Rather, cyclohex-1-ene-1-carboxyl-CoA is hydrated to 2-hydroxycyclohexane-1-carboxyl-CoA.