Pathways of glutamine deamination and their control in the rat kidney

Abstract

An attempt was made to determine the relative activities of phosphate-dependent glu-taminase (PDG), phosphate-independent glutaminase (PIG), and glutamine-ketoacid amino-transferase (GKA) under conditions existing in the rat kidney. Levels of metabolites involved in these 3 pathways were assayed in quick-frozen kidneys. PDG and PIG activities assayed at physiological concentrations of reactants and products were approximately 10-fold greater than GKA activity and could account for the rate of ammonia excretion observed in vivo. Changes in concentrations of metabolites during metabolic acidosis were in directions to elevate PDG activity but lower GKA activity. Deamination of glutamine by kidney slices was inhibited 43% by 10-3 [image] 6-diazo-5-oxo-L-nor-leucine, a glutamine antimetabolite which inhibits PDG and PIG activities about 42% but has little effect on GKA activity. These results suggest that PDG and PIG but not GKA play a significant role in renal glutamine deamination and ammonia production in the rat kidney.