IUPAC - IUB C ommission on Biochemical Nomenclature ( CBN )

The first naturally occurring form of vitamin B6 was isolated in 1938. It has the structure, confirmed by chemical synthesis (1939), of 3-hydroxy-4,5-bis(hydroxymethyl)-2-methylpyridine (I; R = -CHzOH). The trivial name “pyridoxine,” proposed for this compound by P. GyGrgy, came into general use as a synonym for “vitamin Be.” Two other natural compounds possessing vitamin B6 activity, detected in 1944 and recognized as the aldehyde, or 4-formyl analogue (I; R = -CHO) of pyridoxine, and the corresponding amine, or 4-aminomethyl analogue (I; R = -CH2NH2), were designated “pyridoxal” and “pyridoxamine,” respectively. Within the next few years, I. C. Gunsalus, E. E. Snell, A. E. Braunstein, and others demonstrated that a phosphorylated derivative of pyridoxal, later identified as pyridoxal5’-phosphate (II; R = -CHO), is the coenzyme of a large group of specific enzymes catalyzing reactions of amino group transfer, decarboxylation, and other metabolic transformations of individual amino acids. In the course of enzymic transamination, pyridoxal 5’.phosphate undergoes reversible conversion into pyridoxamine 5’-phosphate (II; R = -CH,NH2), which has coenzyme activity for the aminotransferases (EC 2.6.1. -), but not for other types of vitamin BG-dependent enzymes (2, 3). In the IUPAC DeJinitive Rules for the Nomenclature of Vitamins, published in 1960 (4), the term “pyridoxine” was recommended as a generic designation of the B, vitamins, and “pyridoxol” as the trivial name for the alcohol form (I; R = -CH20H) previously designated as pyridoxine (Rule V-7). In the IUPAC-IUB Tentative Rules of 1966 (1) for the nomenclature of vitamins and related compounds (Rule M-7. l), it was suggested that the latter compound should be designated “pyridoxine” or “pyridoxol.” One regrettable consequence of these conflicting recommendations, giving rise to justified criticism, is the continuing use of the word “pyridoxine” in two different meanings-as a generic term for substances with vitamin Bs activity, and as the trivial name of a definite chemical compound (which, incidentally, is