title: Metabolism of valine and 3-methyl-2-oxobutanoate by the isolated perfused rat kidney.
abstract: Metabolism of branched-chain amino and 2-oxo acids was studied in the isolated perfused kidney. Significant amounts of 2-oxo acids were released by perfused kidney with all concentrations of amino acids tested (0.1-1.0 mM each), despite the high activity of branched-chain 2-oxo acid dehydrogenase in kidney. As perfusate valine concentration was increased from 0.2 to 1.0 mM, [1-14C]valine transamination (2-oxo acid oxidized + released) increased roughly linearly; [1-14C]valine oxidation, however, increased exponentially. Increasing perfusate concentration of 3-methyl-2-oxo[1-14C]butanoate from 0 to 1.0 mM resulted in a linear increase in the rate of its oxidation and a rise in perfusate valine concentration; at the same time significant decreases occurred in perfusate isoleucine and leucine concentrations, with corresponding increases in rates of release of their respective 2-oxo acids. Comparison of rates of oxidation of [1-14C]valine and 3-methyl-2-oxo[1-14C]butanoate suggests that 2-oxo acid arising from [1-14C]valine transamination has freer access to the 2-oxo acid dehydrogenase than has the 2-oxo acid from the perfusate. The observations indicate that, when branched-chain amino and 2-oxo acids are present in perfusate at near-physiological concentrations, rates of transamination of the amino and 2-oxo acids by isolated perfused kidney are greater than rates of oxidation.
mesh_terms: D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide); D000818:Animals; D045782:Hemiterpenes; D066298:In Vitro Techniques; D007532:Isoleucine / Q000378:metabolism; D007651:Keto Acids / Q000378:metabolism*; D007658:Ketone Oxidoreductases / Q000378:metabolism; D007668:Kidney / Q000201:enzymology / Q000378:metabolism*; D007930:Leucine / Q000378:metabolism; D008297:Male; D009097:Multienzyme Complexes / Q000378:metabolism; D010084:Oxidation-Reduction; D010477:Perfusion; D051381:Rats; D014633:Valine / Q000378:metabolism*
chemical_list: D045782:Hemiterpenes; D007651:Keto Acids; D009097:Multienzyme Complexes; D007532:Isoleucine; C016211:alpha-keto-beta-methylvaleric acid; C001505:alpha-ketoisovalerate; C013082:alpha-ketoisocaproic acid; D007658:Ketone Oxidoreductases; D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide); D007930:Leucine; D014633:Valine