The utilization of riboflavin antagonists by a mutant of Lactobacillus casei

Covalent bonding of riboflavin homologs by hepatic mitochondrial membrane enzymes

Radioactive riboflavin and homologs of riboflavin possessing an ethyl group in positions 7- or 8-, or both were used to investigate the covalent bonding of the flavins. No strict correlation could be found between the location of the ethyl group and the activities of the enzymes known to be covalently-bound flavoproteins. It is proposed that the widely varying activities of these enzymes when utilizing certain homologs is the result of a combination of the abnormal flavin coenzyme and the differences in the specificity of the apoenzymes in the various tissues.

Riboflavin analogs utilized for metabolism by a Lactobacillus casei mutant

Several new halogen-containing riboflavin analogs that are antagonists for the stock strain of Lactobacillus casei have been found to be utilized by a mutant strain of the microorganism for growth and acid production. Riboflavin analogs consisting of all combinations of a single aliphatic group (methyl or ethyl) and a single halogen group (chloro or bromo) in positions 7 and 8 of the isoalloxazine nucleus possess this property. The analog devoid of substituents in positions 7 and 8 and the analog possessing a methyl group in position 7 and a cysteinyl group in position 8, were inert for both strains of the microorganism.