Transport of amino acids for glutathione biosynthesis in human and dog red cells.

Cysteine and glycine for glutathione biosynthesis in human red cells enter via specific amino acid transport systems, principally system ASC and gly respectively. In contrast, human red cells are impermeable to glutamate, but glutamine enters via a Na-dependent, saturable pathway, which apparently obeys Michaelis-Menten kinetics with appKm and Vmax values of 90-160 microM and 140-240 mumol/1.cells/h respectively. Dog red cells however, do show a Na-dependent glutamate uptake which apparently obeys Michaelis-Menten kinetics with appKm and Vmax values of 4-6 microM and 70-110 mumol/1.cells/h respectively.