Effects on plasma amino acid concentrations and hepatic branched-chain alpha-keto acid dehydrogenase activity of feeding rats diets containing 9 or 50% casein.
Plasma concentrations of amino acids and alpha-ketoisocaproate and alpha-keto-gamma- methiolbutyrate decarboxylation activities in livers of rats trained to eat 9 or 50% casein diets for 5 hours/day, were measured one-half hour before and one-half and 3 hours after the start of the feeding period. Decarboxylation of both alpha-ketoisocaproate and alpha-keto-gamma- methiolbutyrate by liver increased significantly within one-half hour after rats had ingested either the 9 or the 50% casein diet. Liver decarboxylation activity of rats fed the 50% casein diet was from two- to fivefold higher than that of rats fed the 9% casein diet. The greatest difference was observed when calcium, NAD and coenzyme A were included in the decarboxylation assay medium. Although the activity of the branched-chain alpha-keto acid dehydrogenase increased in response to food ingestion, plasma concentrations of branched-chain amino acids also increased greatly after the ingestion of food. The similarity in the responses of alpha-ketoisocaproate and alpha-keto-gamma- methiolbutyrate decarboxylation in rats fed diets differing in protein content and subjected to different feeding regimens allows us to suggest that the branched-chain alpha-keto acid dehydrogenase is responsible, in part, for the oxidative decarboxylation of the alpha-keto acid analog of methionine. J. Nutr . 114: 1025-1034, 1984.
D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide); D000596:Amino Acids / Q000097:blood*; D000818:Animals; D002364:Caseins / Q000494:pharmacology*; D004044:Dietary Proteins / Q000494:pharmacology*; D006128:Growth; D007651:Keto Acids / Q000378:metabolism; D007658:Ketone Oxidoreductases / Q000378:metabolism*; D008099:Liver / Q000201:enzymology*; D008297:Male; D008715:Methionine / Q000031:analogs & derivatives / Q000378:metabolism; D009097:Multienzyme Complexes / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D000596:Amino Acids; D002364:Caseins; D004044:Dietary Proteins; D007651:Keto Acids; D009097:Multienzyme Complexes; C014632:2-keto-4-methylthiobutyric acid; C013082:alpha-ketoisocaproic acid; D008715:Methionine; D007658:Ketone Oxidoreductases; D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)