The oxidation of hypotaurine to taurine: bis-aminoethyl-alpha-disulfone, a metabolic intermediate in mammalian tissue.

Abstract

The primary mammalian metabolic pathway leading to taurine is generally recognized as beginning with the oxidation of cysteine to cysteine sulfinate via cysteine dioxygenase (19). This rate limiting enzyme is, carefully regulated thus setting the rate for the catabolism of sulfur amino acids (4). A major portion of cysteine sulfinate is subject to unidirectional transamination leading to pyruvate and sulfite; a smaller fraction of cysteine sulfinate is decarboxylated by cysteine sulfinate decarboxylase to hypotaurine (8). The ratio of the two pathways appears to be relatively constant; what controls the pathway bifurcation remains unknown. Although a small fraction (10%) of the hypotaurine is subject to unidirectional transamination to acetaldehyde and sulfate (4,6), the bulk of hypotaurine is oxidized to taurine. A possible alternate metabolic route involves initial oxidation of cysteine sulfinate to cysteic acid by an unspecified mechanism followed by decarboxylation of cysteic acid to taurine. The latter is an established capacity of the enzyme cysteine sulfinate decarboxylase (10).