Reactivating chaperones for coenzyme B12-dependent diol and glycerol dehydratases and ethanolamine ammonia-lyase

Tetsuo Toraya, Takamasa Tobimatsu, Naoki Shibata, Koichi Mori

Research output: Chapter in Book/Report/Conference proceedingChapter


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.

Original languageEnglish
Title of host publicationCoenzyme B Enzymes Part A
EditorsE. Neil G. Marsh
PublisherAcademic Press Inc.
Number of pages42
ISBN (Print)9780323915915
Publication statusPublished - Jan 2022

Publication series

NameMethods in Enzymology
ISSN (Print)0076-6879
ISSN (Electronic)1557-7988


  • Adenosylcobalamin
  • Chaperone
  • Coenzyme B12
  • Coenzyme recycling
  • Diol dehydratase
  • Ethanolamine ammonia-lyase
  • Glycerol dehydratase
  • Reactivase
  • Reactivating factor
  • Subunit swapping

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology


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