EFFECTS ON PLASMA AMINO-ACID-CONCENTRATIONS AND HEPATIC BRANCHED-CHAIN ALPHA-KETO ACID DEHYDROGENASE-ACTIVITY OF FEEDING RATS DIETS CONTAINING 9 PERCENT OR 50 PERCENT CASEIN

被引:28
作者
DIXON, JL
HARPER, AE
机构
[1] UNIV WISCONSIN, COLL AGR & LIFE SCI, DEPT BIOCHEM, MADISON, WI 53706 USA
[2] UNIV WISCONSIN, COLL AGR & LIFE SCI, DEPT NUTR SCI, MADISON, WI 53706 USA
关键词
D O I
10.1093/jn/114.6.1025
中图分类号
R15 [营养卫生、食品卫生]; TS201 [基础科学];
学科分类号
100403 ;
摘要
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 h/day, were measured 1/2 h before and 1/2 and 3 h after the start of the feeding period. Decarboxylation of both .alpha.-ketoisocaproate and .alpha.-keto-.gamma.-methiolbutyrate by liver increased significantly within one-half after rats had ingested either the 9 or the 50% casein diet. Liver decarboxylation activity of rats fed the 50% casein diet was from 2-5-fold higher than that of rats fed the 9% casein diet. The greatest difference was observed when Ca, NAD and CoA 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 for the suggestion that the branched-chain .alpha.-keto acid dehydrogenase is responsible, in part, for the oxidative decarboxylation of the .alpha.-keto acid analog of methionine.
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页码:1025 / 1034
页数:10
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