Document Detail

Activities of branched-chain amino acid--degrading enzymes in liver from rats fed different dietary levels of protein.
MedLine Citation:
PMID:  2778545     Owner:  NLM     Status:  MEDLINE    
The relationships among dietary protein intake, plasma branched-chain amino acid (BCAA) and keto acid (BCKA) concentrations, and liver BCAA-degrading enzyme activities were investigated in rats fed, for 5 h/d for 2, 6 or 9 d, diets containing from 0 to 50% casein. Plasma, liver and muscle BCAA concentrations were proportional to protein intake over the entire range tested; plasma BCKA concentration, however, was proportional only in the range from 0 to 20% casein, after which a plateau was reached. By d 2, liver cytosolic BCAA aminotransferase activity had increased in rats fed 50% casein; by d 9, activity had increased in rats fed 0 or 5% casein as well. Liver mitochondrial BCAA aminotransferase activity was unresponsive to dietary treatment. Basal liver BCKA dehydrogenase activity and the percent active complex were proportional to protein intake on d 2 and 6. On d 2, total BCKA dehydrogenase activity was the same in all groups; by d 6, total activity had increased in rats fed 30 or 50% casein. We conclude that although the adaptive changes in BCAA-degrading enzyme activities are small, they are sufficient to compensate for excessively high or low protein intakes, so that tolerable concentrations of BCAA and BCKA are maintained.
S Soemitro; K P Block; P L Crowell; A E Harper
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The Journal of nutrition     Volume:  119     ISSN:  0022-3166     ISO Abbreviation:  J. Nutr.     Publication Date:  1989 Aug 
Date Detail:
Created Date:  1989-10-20     Completed Date:  1989-10-20     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0404243     Medline TA:  J Nutr     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1203-12     Citation Subset:  IM    
Department of Nutritional Sciences, University of Wisconsin, Madison 53706.
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MeSH Terms
3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)
Amino Acids, Branched-Chain / metabolism
Body Weight
Caseins / metabolism
Cytosol / metabolism
Dietary Proteins / pharmacology*
Keto Acids / metabolism
Ketone Oxidoreductases / metabolism*
Liver / enzymology*
Mitochondria, Liver / enzymology
Multienzyme Complexes / metabolism*
Rats, Inbred Strains
Transaminases / metabolism*
Grant Support
Reg. No./Substance:
0/Amino Acids, Branched-Chain; 0/Caseins; 0/Dietary Proteins; 0/Keto Acids; 0/Multienzyme Complexes; EC 1.2.-/Ketone Oxidoreductases; EC Dehydrogenase (Lipoamide); EC 2.6.1.-/Transaminases; EC transaminase

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