Old Yellow enzyme: aromatization of cyclic enones and the mechanism of a novel dismutation reaction.
Old Yellow enzyme: aromatization of cyclic enones and the mechanism of a novel dismutation reaction.
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老黄酶：环烯酮的芳构化和新型歧化反应的机制。
DOI：
10.1021/bi00013a014
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发表时间：
1995
期刊：
影响因子：
2.9
通讯作者：
Massey,V
中科院分区：
文献类型：
--
作者：
Vaz,AD;Chakraborty,S;Massey,V
1995年1月19日接收的修订版Mandarin pt ®摘要：老黄酶与β-不饱和环酮如3-氧代萘烷-4-烯反应产生的电荷转移带的起源（ODE，根据类固醇的惯例编号）、3-氧代十氢化萘-4-烯-10-甲醛（ODBC）和2-环己烯酮的芳构化是由于ODE和ODBC芳构化为3-羟基-6，7，8，9-四氢化萘（HTN）和2-环己烯酮转化为苯酚。ODBC到HTN的芳构化是立体定向的，并且涉及1/3，2a氢的反式脱氢。芳构化在有氧和厌氧条件下发生。除了在有氧条件下的ODBC之外，这些底物的芳构化伴随着歧化反应，其中每个底物的第二分子的烯键被还原以得到饱和环酮。在有氧反应条件下，分子氧可以作为ODEG和其他底物的电子受体。歧化反应涉及氢化物从一个底物分子转移到第二个底物分子的β-碳的整个序列，沿着溶剂质子被β-碳吸收。19-去甲睾酮被芳香化为β-雌二醇;然而，其他3-氧代-A4-类固醇如孕酮、睾酮和雄烯-3，17-二酮与酶紧密结合但不被芳香化。β-不饱和羰基化合物的烯键的NADPH依赖性还原限于醛和酮。3-不饱和酸、酯、酰胺和腈不被还原。NADPH对ODE或肉桂醛的烯键的还原是通过从还原的吡啶核苷酸到β，β-不饱和羰基化合物的β-碳的氢化物转移和β-碳的溶剂质子吸收的整个顺序发生的。NADPH的4-前氢化物在还原反应中转移。β-不饱和醛或酮的NADPH依赖性还原中的结构-功能关系表明，β-碳上烷基取代的增加导致烯键还原速率的显著降低，这与β-碳上氢化物转移的空间位阻一致。最初从啤酒酵母中分离出来（瓦尔堡和克里斯蒂安，1933），在我们对蛋白质作为酶的理解和辅因子在酶学中的作用的演变中有着悠久而辉煌的历史。近年来，蛋白质纯化和分子生物学技术表明OYE由几种同种型组成，由不同的基因编码（Miura等人，1986; Saito等人，1991; Stottet等人，1993年）。OYE 1的晶体结构已在2.0 μ m的分辨率下解析（Fox & Karplus，1993，1994）。尽管对这种酶的物理和生物化学性质有广泛的了解，但其生理学性质仍然是未知的。
Revised Manuscript Received January 19, 1995® abstract: The origin of charge transfer bands that develop on reaction of Old Yellow Enzyme with,/3-unsaturated cyclic ketonessuch as 3-oxodecalin-4-ene (ODE, numbered according to the convention for steroids), 3-oxodecalin-4-ene-10-carboxaldehyde (ODBC), and 2-cyclohexenone is shown to be due to the aromatization of ODE and ODBC to 3-hydroxy-6, 7, 8, 9-tetrahy dronaphthalene (HTN) and of 2-cyclohexenone to phenol. The aromatization of ODBC to HTN is stereospecific and involves the trans dehydrogenation of the 1/3, 2a hydrogens. The aromatization occurs under aerobic as well as anaerobic conditions. With the exception of ODBC under aerobic conditions, the aromatization of these substrates is accompanied by a dismutation reaction in which the olefinic bond of a second molecule of each substrate is reduced to give the saturated cyclic ketone. Molecular oxygen may serve as the electron acceptor with ODEG and some other substrates under aerobic reaction conditions. The dismutation reaction involves an overall sequence of hydride transfer from one substrate molecule to the/8-carbon of a second substrate molecule along with a solvent proton uptake by the-carbon. 19-Nortestosterone is aromatized to/3-estradiol; however, other 3-oxo-A4-steroids such as progesterone, testosterone, and androstene-3, 17-dione bind tightly to the enzyme but are not aromatized. The NADPH-dependent reduction of the olefinic bond of,/3-unsaturated carbonyl compounds is limited to aldehydes and ketones.,/3-Unsaturated acids, esters, amides, and nitriles are not reduced. The reduction of the olefinic bond of ODE or cinnamaldehyde by NADPH occurs by an overall sequence of hydride transfer from the reduced pyridine nucleotide to the/8-carbon of the,/3-unsaturatedcarbonyl compound and a solvent proton uptake by the-carbon. The 4-pro-hydride of NADPH is transferred in the reduction reaction. Structure-function relationships in the NADPH-dependent reduction of,/3-unsaturated aldehydes or ketones indicate that increasing alkyl substitution at the/8-carbon results in marked decrease in the rate of reduction of the olefinic bond, consistent with a steric hindrance to hydride transfer at the/3-carbon.Old Yellow Enzyme (OYE), 1 the first discovered fla-voprotein, isolated originally from Brewer’s Bottom Yeast (Warburg & Christian, 1933) has had a long and illustrious history in the evolution of our understanding of proteins as enzymes and the role of cofactors in enzymology. OYE has in recent years been shownby protein purification and molecular biological techniques to consist of several isoforms, encoded by separate genes (Miura et al., 1986; Saito et al., 1991; Stottet al., 1993). The crystal structure of OYE 1 has been solved at a resolution of 2.0 Á (Fox & Karplus, 1993, 1994). Despite an extensive knowledge of the physical and biochemical properties of this enzyme, its physiological