Bovine erythrocyte glutathione S-transferase: purification, inhibition, and complex formation

Glutathione S-transferase has been purified from bovine erythrocytes by affinity chromatography. The enzyme has an isoelectric point of 7.2, behaves as a 48-kDa protein composed of two identical subunits, and has an N-terminal sequence of PPYTIVYFPVQGR?EAMRMLL. This sequence, the amino acid composition, and the kinetic parameters suggest that the enzyme belongs to the pi-class of transferases. Hemins, porphyrins, and fatty acids form complexes with the enzyme and serve as effective inhibitors. Treatment of the transferase with N-ethylmaleimide, 3-amino-1,2,4-triazole, diethyl pyrocarbonate, or 2,3-butanedione inhibits transferase activity without altering tetrapyrrole binding. The role of the complexation and inhibition of glutathione S-transferase in erythroid metabolism has yet to be elucidated.