腺苷钴胺
辅因子
生物化学
酶
化学
辅酶A
伴侣(临床)
裂解酶
还原酶
医学
病理
作者
Tetsuo Toraya,Takamasa Tobimatsu,Naoki Shibata,Kōichi Mori
出处
期刊:Methods in Enzymology
日期:2022-01-01
卷期号:: 243-284
标识
DOI:10.1016/bs.mie.2021.11.028
摘要
Adenosylcobalamin (AdoCbl) or coenzyme B12-dependent enzymes tend to undergo mechanism-based inactivation during catalysis or inactivation in the absence of substrate. Such inactivation may be inevitable because they use a highly reactive radical for catalysis, and side reactions of radical intermediates result in the damage of the coenzyme. How do living organisms address such inactivation when enzymes are inactivated by undesirable side reactions? We discovered reactivating factors for radical B12 eliminases. They function as releasing factors for damaged cofactor(s) from enzymes and thus mediate their exchange for intact AdoCbl. Since multiple turnovers and chaperone functions were demonstrated, they were renamed "reactivases" or "reactivating chaperones." They play an essential role in coenzyme recycling as part of the activity-maintaining systems for B12 enzymes. In this chapter, we describe our investigations on reactivating chaperones, including their discovery, gene cloning, preparation, characterization, activity assays, and mechanistic studies, that have been conducted using a wide range of biochemical and structural methods that we have developed.
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