Assessment of effects of amino acids and branched chain keto acids on leucine oxidation in human lymphocytes

Abstract

Effects of amino acids and branched chain keto acids on leucine transamination and oxidation were assessed in peripheral human lymphocytes. Isoleucine (80–200 μmol/l) and valine (250–500 μmol/l) diminished transamination and oxidation of leucine up to 25%, glutamine (50–1000 umol/l) up to 55%. α-Ketoisocaproic acid (KIC; 200 μmol/l) augmented the activity state of branched chain keto acid dehydrogenase by 40%. It is concluded that in peripheral human lymphocytes (1) isoleucine, valine and glutamine are physiological inhibitors of leucine catabolism, and (2) leucine can promote its own degradation via KIC.

Key Words:

• branched chain keto acid dehydrogenase
• glutamine
• human lymphocytes
• KIC