Characterization and Mechanism of Action of a Reactivating Factor for Adenosylcobalamin-dependent Glycerol Dehydratase

Hideki Kajiura, Koichi Mori, Takamasa Tobimatsu, Tetsuo Toraya

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64 Citations (Scopus)


Adenosylcobalamin-dependent glycerol dehydratase undergoes mechanism-based inactivation by its physiological substrate glycerol. We identified two genes (gdrAB) of Klebsiella pneumoniae for a glycerol dehydratase-reactivating factor (Tobimatsu, T., Kajiura, H., Yunoki, M., Azuma, M., and Toraya, T. (1999) J. Bacteriol. 181, 4110-4113). Recombinant GdrA and GdrB proteins formed a tight complex of (GdrA)2(GdrB)2, which is a putative reactivating factor. The purified factor reactivated the glycerol-inactivated and O2-inactivated glycerol dehydratases as well as activated the enzyme-cyanocobalamin complex in vitro in the presence of ATP, Mg2+, and adenosylcobalamin. The factor mediated the exchange of the enzyme-bound, adenine-lacking cobalamins for free, adenine-containing cobalamins in the presence of ATP and Mg2+ through intermediate formation of apoenzyme. The factor showed extremely low ATP-hydrolyzing activity and formed a tight complex with apoenzyme in the presence of ADP. Incubation of the enzyme-cyanocobalamin complex with the reactivating factor in the presence of ADP brought about release of the enzyme-bound cobalamin. The resulting tight inactive complex of apoenzyme with the factor dissociated upon incubation with ATP, forming functional apoenzyme and a low affinity form of factor. Thus, it was established that the reactivation of the inactivated holoenzymes takes place in two steps: ADP-dependent cobalamin release and ATP-dependent dissociation of the apoenzyme-factor complex. We propose that the glycerol dehydratase-reactivating factor is a molecular chaperone that participates in reactivation of the inactivated enzymes.

Original languageEnglish
Pages (from-to)36514-36519
Number of pages6
JournalJournal of Biological Chemistry
Issue number39
Publication statusPublished - Sept 28 2001

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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