Some problems concerning the determination of different corrinoids by the plate method with Escherichia coli 113-3.

Abstract

Biological activity of some vitamin B12 forms for Escherichia coli 113-3 and the effect of methionine on the assay of these compounds by E. coli 113-3 were studied. It was found that the coenzymatic form had the highest biological activity and that under experimental conditions methionine was an interfering factor in determination of the coenzymatic form and the methyl derivative of B12 only. Otherwise, metionine did not affect the determination of cyanocobalamin an hydroxycobalamin even when the methionine and vitamin B12 ratio was 32 000 : 1.