The γ-Glutamyl Cycle: A Possible Transport System for Amino Acids

TLDR: Evidence is presented that rat kidney contains enzymes that catalyze the synthesis and utilization of glutathione and these reactions, which involve the uptake and release of amino acids from γ-glutamyl linkage, constitute a cyclical process, which has properties that fulfill the requirements of an amino acid transport system.

Abstract: Evidence is presented that rat kidney contains enzymes that catalyze the synthesis and utilization of glutathione; these reactions, which involve the uptake and release of amino acids from γ-glutamyl linkage, constitute a cyclical process which is termed „the γ-glutamyl cycle.” The γ-glutamyl cycle has properties that fulfill the requirements of an amino acid transport system. Thus, γ-glutamyl transpeptidase may function in translocation and γ-glutamylcysteine synthetase and glutathione synthetase may catalyze energy-requiring „recovery” steps in transport. These and other considerations suggest that glutathione serves a carrier function in amino acid transport.