Vitamin B6: a long known compound of surprising complexity

Abstract

In recent years vitamin B6 has become a focus of research describing the compound's critical function in cellular metabolism and stress response. For many years the sole function of vitamin B6 was considered to be that of an enzymatic cofactor. However, recently it became clear that it is also a potent antioxidant that effectively quenches reactive oxygen species and is thus of high importance for cellular well-being. In view of the recent findings, the current review takes a look back and summarizes the discovery of vitamin B6 and the elucidation of its structure and biosynthetic pathways. It provides a detailed overview on vitamin B6 both as a cofactor and a protective compound. Besides these general characteristics of the vitamin, the review also outlines the current literature on vitamin B6 derivatives and elaborates on recent findings that provide new insights into transport and catabolism of the compound and on its impact on human health.

Figure 1

Schematic drawing of de novo and salvage pathways.

Figure 2

Bacterial catabolic pathways of vitB6. Roman numbers in parenthesis indicate enzymes: (I) pyridoxine 4-oxidase; (II) pyridoxal phosphatase; (III) pyridoxal 4-dehydrogenase; (IV) 4-pyridoxollactonase; (V) pyridoxol oxidase. Arabic numbers indicate compound: (1) PN; (2) PLP; (3) PL; (4) 4-pyridoxolactone; (5) 4-pyridoxic acid; (6) succinic semialdehyde (modified from [62]).