Purification and characterization of hepatic glutathione S-transferases of rhesus monkeys. A family of enzymes similar to the human hepatic glutathione S-transferases

Abstract

Thirteen forms of glutathione S-transferase were purified from the livers of female rhesus monkeys (Macaque mulatta). Most (74.7%) of the activity in the hepatic cytosol adhered well to the GSH affinity column and could be eluted only with the addition of GSH to the eluting buffer. The predominant isoenzymes (n = 5) in this ‘high-affinity’ fraction had alkaline pI values (greater than 9.0) and contained a subunit with an Mr value of 24,000. All of these isoenzymes had high organic peroxidase activity and, on the basis of amino acid analysis, substrate specificities and affinity for non-substrate ligands, appear to belong to the family of glutathione S-transferases that have been termed alpha [Mannervik, Alin, Guthenberg, Jensson, Tahir, Warholm & Jörnvall (1985) Proc. Natl. Acad. Sci. U.S.A. 82, 7202-7206]. Also within the high-affinity fraction was an isoenzyme with an acidic (5.8) pI value. This acidic isoenzyme was composed of a unique subunit (Mr 23,000). The N-terminal sequence (ten residues) of this acidic enzyme was identical with that of a human form that is referred to as pi. The predominant form of enzyme in the ‘low-affinity’ (eluted from the GSH affinity column with an increase in buffer pH) fraction was a homodimer of a 26,000-Mr subunit. It had an alkaline pI (greater than 9.0) but it lacked organic peroxidase activity. The N-terminal sequence (ten residues) of this enzyme was identical with that of a human enzyme referred to as mu. The substrate specificities and affinity for non-substrate ligands of this monkey enzyme also were similar to those of the human enzyme. In conclusion, the liver cytosol of rhesus monkeys contains a number of glutathione S-transferase isoenzymes that are very similar to the human hepatic enzymes.