プリン系塩基含有補酵素型ビタミンB_<12>のグルタミン酸異性化反応における特異性について

概要

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Comparative study was made on the affinity to glutamate mutase of cobamide coenzyme analogues containing several purine derivatives. Glutamate mutase was partially purified from the cultures of Clostridium tetanomorphum. Purinylcobamide coenzyme (PCC), 2-chloroadenylcobamide coenzyme (CACC), 2-thioadenylcobamide coenzyme (TACC) and 6-methylmercaptopurinylcobamide coenzyme (MPCC) were prepared from the cells of Propionibacterium arabinosum incubated with the respective purine derivatives. The Michaelis constants of cobamide coenzymes tested in the anaerobic glutamate mutase reaction based on the conversion of β-methylaspartic acid to glutamic acid were determined by microbiological assay method for glutamic acid formed. The K_m values of PCC, CACC, TACC, MPCC and cobalamin coenzyme were 11.6×10^<-7>, 2.3×10^<-7>, 5.9×10^<-7>, 10.9×10^<-7> and 9.3×10^<-7>M, respectively. Little or no difference was observed in V_<max> values among the cobamide coenzymes tested. The finding suggests that the kind of base, a lower ligand in vitamin B_<12> molecule, may play some role in the binding affinity of vitamin B_<12> to the apoenzyme, but there may be no special tendency in purine bases as compared with benzimidazoles.
日本ビタミン学会の論文
1975-01-25