A history of the isolation and identification of vitamin B(6).

In the 1930s, Rudolf Peters showed that young rats kept on a semi-synthetic diet with added thiamin and riboflavin but no other supplement developed 'rat acrodynia', a condition characterized by severe cutaneous lesions. In 1934, Paul György showed that the factor which cured 'rat acrodynia' was vitamin B(6). Other studies soon showed that vitamin B(6) deficiency produced convulsions in rats, pigs, and dogs, and a microcytic anemia in certain animals. Samuel Lepkovsky isolated and crystallized vitamin B(6) in 1938. The following year, Leslie Harris and Karl Folkers, and Richard Kuhn and his associates independently showed that vitamin B(6) was a pyridine derivative, 3-hydroxy-4,5-dihydroxy-methyl-2-methyl-pyridine. György proposed the term pyridoxine for this derivative. Esmond Snell developed a microbiological growth assay in 1942 that led to the characterization of pyridoxamine, the animated product of pyridoxine, and pyridoxal, the formyl derivative of pyridoxine. Further studies showed that pyridoxal, pyridoxamine, and pyridoxine have largely equal activity in animals and owe their vitamin activity to the ability of the organism to convert them into the enzymatically active form pyridoxal-5-phosphate. Pyridoxal-5-phosphate plays a role in a wide variety of enzyme systems, especially in the metabolic utilization and transformation of amino acids.

Esmond E. Snell--the pathfinder of B vitamins and cofactors.

Esmond E. Snell (1914-2003) was a giant of B-vitamin and enzyme research. His early research in bacterial nutrition had lead to the discovery of vitamins such as lipoic acid and folic acid, and an anti-vitamin avidin. He developed microbiological assay methods for riboflavin and other vitamins and amino acids, which are still used today. He also investigated the metabolism of vitamins, discovered pyridoxal and pyridoxamine as the active forms of vitamin B(6) and revealed the mechanism of transamination and other reactions catalysed by vitamin B(6) enzymes. His research in later years on pyruvoyl-dependent histidine decarboxylase unveiled the biogenesis mechanism of this first built-in cofactor. Throughout his career, he was a great mentor of many people, all of whom are inspired by his philosophy of science.