[Inhibition of pyridoxal kinase by 2- and 6-alkyl substituted vitamin B6 analogues and by pyridoxal oximes].

It is shown in the system with partially purified pyridoxal kinase from mouse liver, that the presence of one alkyl group in the 2nd or 6th positions of pyridine cycle in pyridoxole and pyridoxamine derivatives and pyridoxal oximes is a necessary condition which determines relatively high affinity of structural vitamin B6 analogues to the enzyme. 2'-n-Propylpyridoxal was phosphorylated by pyridoxal kinase with a relatively high rate, while 2-nor-6-methylpyridoxal, having a similar affinity to pyridoxal kinase, was not phosphorylated at all. The data obtained indicate an important role of the methyl group in the 2nd position of pyridine cycle in vitamin B6 molecule for its fixation in the enzyme active site and for the proper orientation, which provides enzymatic substrate phosphorylation. Some structural peculiarities of vitamin B6 analogues are considered, pre-determining their low or high efficiency as vitamin B6 antimetabolite in vivo.