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.