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胆汁酸生合成における炭素-炭素結合切断反応に関する研究

胆汁酸生物合成中碳-碳键断裂反应的研究

基本信息

批准号：
09672155
负责人：
MORISAKI Masuo
金额：
$ 1.47万
依托单位：
Kyoritsu College of Pharmacy
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09672155/
关键词：
Bile acid Cholic acid Cholesterol Biosynthesis β-Oxidation Carbon-carbon bond cleavage reaction Ethyl ketone コール酸生合成 24-オキソ-THCA CoAエステルチオリシス反応 CoA β-ケトチオエステル HepG2

项目摘要

Cholic acid biosynthesis from cholesterol involves C-24/C-25 bond cleavage.A precursor of this carbon-carbon bond cleavage reaction is 3α, 7α, 12α-trihydroxycoprostan-26-oic acid(THCA) and this acid is thought to be metabolized into cholic acid by a mechanism similar to that of the β-oxidation of fatty acids. Among the intermediates, experimental evidence for the intermediary role of THCA-CoA, 24-ene-THCA-CoA and 24-hydroxy-THCA-CoA has been accumulated. In contrast, little has been known on the formation and metabolism of 24-oxo-THCA-CoA. Our efforts on this line are described here.The potential substrates including the three THCA-CoA derivatives mentioned above were chemically synthesized, and incubated with rat liver light mitochondria fraction or Hep G2. 24-Oxo-THCA-CoA, if produced during incubation, should be transformed into 27-nor-3α, 7α, 12α-trihydroxy-24-coprostan-24-on ("ethyl ketone") by the subsequent alkaline treatment inducing facile decarboxylation of the intermediate β-keto-carboxylic acid. GC-MS analysis of the trimethylsilyl ether derivatives coming from THCA-CoA, 24-ene-THCA-CoA and 24- hydroxy-THCA CoA clearly detected the "ethyl ketone". These results indicated the enzymic transformation of these three CoA-esters into 24-oxo-THCA-CoA.Similarly 24-oxo-THCA-CoA was incubated and the subsequent HPLC analysis of the p-bromophenacyl ester derivative indicated the enzymic formation of cholic acid(or cholyl-CoA from 24-oxo-THCA-CoATaken together, it is concluded that 24-oxo-THCA-CoA is the final intermediate of cholic acid biosynthesis.

从胆固醇合成胆酸涉及到C-24/C-25键的断裂。这种碳-碳键裂解反应的前体是3α， 7α， 12α-三羟基钴蛋白酶-26-酸（THCA），这种酸被认为通过类似于脂肪酸β-氧化的机制代谢成胆酸。在中间体中，THCA-CoA、24-烯-THCA-CoA和24-羟基THCA-CoA的中间作用的实验证据已经积累。相比之下，对24-oxo-THCA-CoA的形成和代谢知之甚少。这里描述了我们在这方面的努力。化学合成包括上述三种THCA-CoA衍生物在内的潜在底物，并与大鼠肝脏轻线粒体部分或Hep G2孵育。24-Oxo-THCA-CoA如果在孵育过程中产生，应通过随后的碱处理诱导中间β-酮羧酸的易脱羧，转化为27-no -3α， 7α， 12α-三羟基-24- coprostan24 -on（“乙基酮”）。对THCA-CoA、24-烯-THCA-CoA和24-羟基-THCA-CoA的三甲基硅基醚衍生物进行气相色谱-质谱分析，明确检测到“乙基酮”。这些结果表明，这三种辅酶a酯酶转化为24-氧- thca -辅酶a。同样，对24-氧- thca - coa进行孵育，随后对对溴苯酰酯衍生物的HPLC分析表明，24-氧- thca - coa在酶促下形成胆酸（或胆酰coa），由此得出24-氧- thca - coa是胆酸生物合成的最终中间体。