title: Effects of diet and of alloxan-diabetes on the activity of branched-chain 2-oxo acid dehydrogenase complex and of activator protein in rat tissues.
abstract: The total activities (sum of active and inactive forms) of branched-chain 2-oxo acid dehydrogenase complex in tissues of normal rats fed on a standard diet were (unit/g wet wt.): liver, 0.82; kidney, 0.77; heart, 0.57; hindlimb skeletal muscles, 0.034. Total activity was decreased in liver by 9%- or 0%-casein diets and by 48 h starvation, but not by alloxan-diabetes. Total activities were unchanged in kidney and heart. The amount of active form of the complex (in unit/g wet wt. and as % of total) in tissues of normal rats fed on standard diet was: liver, 0.45, 55%; kidney, 0.55, 71%; heart, 0.03, 5%; skeletal muscle less than 0.007, less than 20% (below lower limit of assay). The concentration of the active form of the complex was decreased in liver and kidney, but not in heart, by low-protein diets, 48 h starvation and alloxan-diabetes. In heart muscle alloxan-diabetes increased the concentration of active complex. The concentration of activator protein (which activates phosphorylated complex without dephosphorylation) in liver and kidney was decreased by 70-90% by low-protein diets and 48 h starvation. Alloxan-diabetes decreased activator protein in liver, but not in kidney. Evidence is given that in tissues of rats fed on a normal diet approx. 70% of whole-body active branched chain complex is in the liver and that the major change in activity occasioned by low-protein diets is also in the liver.
mesh_terms: D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide); D000818:Animals; D002458:Cell Fractionation; D003921:Diabetes Mellitus, Experimental / Q000201:enzymology*; D004032:Diet; D004789:Enzyme Activation / Q000187:drug effects; D005459:Fluorides / Q000494:pharmacology; D066298:In Vitro Techniques; D007651:Keto Acids / Q000494:pharmacology; D007658:Ketone Oxidoreductases / Q000378:metabolism*; D008297:Male; D008928:Mitochondria / Q000201:enzymology; D008930:Mitochondria, Liver / Q000201:enzymology; D009097:Multienzyme Complexes / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D014018:Tissue Distribution
chemical_list: D007651:Keto Acids; D009097:Multienzyme Complexes; C013082:alpha-ketoisocaproic acid; D007658:Ketone Oxidoreductases; D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide); D005459:Fluorides