Rats with vitamin B6 deficiency excrete cystathionine in the urine (Hope, 1957). Cystathionine is an amino acid in the pathway of synthesis of cysteine from methionine (Fig. 1). A methyl group is removed from methionine to produce homocysteine, which condenses with serine to yield cystathionine. This condensation is catalysed by a transulphurase enzyme requiring pyridoxal phosphate as a co-enzy...

Despite intensive effort, the majority of the annotated Mycobacterium tuberculosis genome consists of genes encoding proteins of unknown or poorly understood function. For example, there are seven conserved hypothetical proteins annotated as homologs of pyridoxine 5'-phosphate oxidase (PNPOx), an enzyme that oxidizes pyridoxine 5'-phosphate (PNP) or pyridoxamine 5'-phosphate (PMP) to form pyrid...

Incubation with bromopyruvate did not cause appreciable inactivation of either supernatant or mitochondrial isozyme of aspartate aminotransferase from pig heart. In the presence of either L-cysteine sulfinate or L-aspartate, however, bromopyruvate rapidly inactivated both isozymes. Bromopyruvate also acted as a keto acid substrate in the conversion of the pyridoxamine form of both enzymes to th...

The B-vitamins include thiamin (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), the B6 complex (pyridoxal, pyridoxamine, pyridoxine), biotin (B8 or Vitamin H), folic acid (B9), and B12. Each of the B-vitamins plays a key role as either an enzymatic cofactor or metabolic constituent in many facets of intermediary metabolism. For example, about half of the propionate that reaches the ru...