In Vitro Hydrolysis of Zinc Chlorophyllide a Homologues by a BciC Enzyme,Biochemistry

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In Vitro Hydrolysis of Zinc Chlorophyllide a Homologues by a BciC Enzyme
Biochemistry ( IF 2.9 ) Pub Date : 2020-12-01 , DOI: 10.1021/acs.biochem.0c00850
Mitsuaki Hirose ₁ , Jiro Harada ₂ , Hitoshi Tamiaki ₁

Affiliation

Chlorosomes in green photosynthetic bacteria are the largest and most efficient light-harvesting antenna systems of all phototrophs. The core part of chlorosomes consists of bacteriochlorophyll c, d, or e molecules. In their biosynthetic pathway, a BciC enzyme catalyzes the removal of the C13²-methoxycarbonyl group of chlorophyllide a. In this study, the in vitro enzymatic reactions of chlorophyllide a analogues, C13²-methylene- and ethylene-inserted zinc complexes, were examined using a BciC protein from Chlorobaculum tepidum. As the products, their hydrolyzed free carboxylic acids were observed without the corresponding demethoxycarbonylated compounds. The results showed that the in vivo demethoxycarbonylation of chlorophyllide a by an action of the BciC enzyme would occur via two steps: (1) an enzymatic hydrolysis of a methyl ester at the C13²-position, followed by (2) a spontaneous (nonenzymatic) decarboxylation in the resulting carboxylic acid.

中文翻译：

BciC酶体外水解叶绿素锌a同系物

绿色光合细菌中的染色体是所有光养生物中最大，最有效的光收集天线系统。叶绿体的核心部分由细菌叶绿素c，d或e分子组成。在其生物合成途径中，BciC酶催化去除叶绿素a的C13 ^2-甲氧羰基。在这项研究中，叶绿素a类似物，C13 ^2-亚甲基和乙烯插入的锌配合物的体外酶促反应，使用了来自温和的Chlorobaculum pidpidum的BciC蛋白进行了研究。。作为产物，在没有相应的脱甲氧基羰基化化合物的情况下观察到它们的水解的游离羧酸。结果表明，通过BciC酶的作用体内叶绿素a的体内脱甲氧基羰基化将通过两个步骤进行：（1）在C13 ²位上甲酯的酶促水解，然后（2）自发地（非酶促））在所得羧酸中脱羧。

更新日期：2020-12-15

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