[Effect of the structure of the nucleoside ligand of cobalamines on their enzymatic properties in a glycerol dehydratase system].

The interaction between 8 adenosyl cobalamine (AdoCbl) analogs modified in adenine and deoxyribose of the nucleoside ligand and glycerol dehydratase from Klebsiella pneumoniae ATCC 25955 was studied. It was found that araadenosyl-, 3-isoadenosyl-, aristeromycyl- and nebularyl cobalamines possess coenzymic properties. The catalytic activities of these analogs complexes with glycerol dehydratase make up to 110, 36, 30 and 6% of the enzyme activity with the natural cofactor AdoCbl. Benzimidazolribosyl-, toyokamycil-, L-adenosyl- and adenosylethyl cobalamines are effective competitive inhibitors with respect to AdoCbl. All AdoCbl analogs have high affinity for the apoenzyme; their Km and Ki values are close to 10(-7)--10(-8) M. The inactivation kinetics of catalytically active glycerol dehydratase complexes in the absence of substrate were studied. The rate of this process was found to depend on the structure of the analogs. It was shown that inversion of the 2'-OH-group of deoxyribose in AdoCbl results in the increase of Km for the substrate (1,2-propanediol). The main parameters of the CD spectra for AdoCbl analogs are described.