EurekaMag.com logo
+ Site Statistics
References:
47,893,527
Abstracts:
28,296,643
+ Search Articles
+ Subscribe to Site Feeds
EurekaMag Most Shared ContentMost Shared
EurekaMag PDF Full Text ContentPDF Full Text
+ PDF Full Text
Request PDF Full TextRequest PDF Full Text
+ Follow Us
Follow on FacebookFollow on Facebook
Follow on TwitterFollow on Twitter
Follow on Google+Follow on Google+
Follow on LinkedInFollow on LinkedIn

+ Translate

Regulation of leucine and alpha keto iso caproate metabolism in skeletal muscle






Journal of Biological Chemistry 253(22): 8126-8133

Regulation of leucine and alpha keto iso caproate metabolism in skeletal muscle

Leucine catabolism by the perfused rat hindquarter was studied by measuring transamination of leucine and the formation and oxidative decarboxylation of .alpha.-ketoisocaproic acid. The perfusate contained 0.10 or 0.50 mM [114C]leucine, all other amino acids at approximately reported rat plasma concentrations and 5.5 mM glucose. Release of a-ketoisocaproic acid by the hindquarter was immediate. By 60 min, .alpha.-ketoisocaproic acid always accounted for 20-30% of the total circulating leucine carbon ([leucine] + [.alpha.-ketoisocaproic acid]). In nonrecirculating perfusions, .alpha.-ketoisocaproic acid release represented 46% of the leucine undergoing transamination. In perfusions with insulin, when [1-14C].alpha.-ketoisocaproic acid was substituted for leucine, the major fate of .alpha.-ketoisocaproic acid was transamination to leucine rather than oxidation. Using a nonrecirculating perfusion with 0.50 mM leucine, the apparent rate of oxidative decarboxylation of [1-14C].alpha.-ketoisocaproic acid was 7.4 nmol .cntdot. g-1 muscle per min (54% of the rate of transamination). With an initial leucine concentration of 0.50 mM in a recirculating perfusion system, .alpha.-ketoisocaproic acid decarboxylation averaged 5.19 nmol .cntdot. g-1 muscle per min. With an initial leucine concentration of 0.10 mM, decarboxylation increased continuously but reached a rate of only 0.88 nmol .cntdot. g-1 muscle per min at the end of 2 h. Insulin addition significantly decreased the rate of decarboxylation and reduced leucine transamination. In the recirculating system with insulin, increasing the initial leucine concentration from 0.10-0.50 mM stimulated net leucine uptake 8- to 9-fold and enhanced oxidation 5- to 15-fold, depending on the time interval. Raising the initial leucine concentration or adding insulin, or both, stimulated net valine and isoleucine uptake by the perfused hindquarter but decreased release of their respective .alpha.-keto acids, .alpha.-ketoisovaleric acid and .alpha.-keto-.beta.-methylvaleric acid. Amino acid concentrations and the hormonal state of the animal influence the extent to which branched-chain .alpha.-keto acids will be oxidized by or released from muscle.


Accession: 006288982

PMID: 711739



Related references

Hutson, S.M.; Zapalowski, C.; Cree, T.C.; Harper, A.E., 1980: Regulation of leucine and alpha keto iso caproic acid metabolism in skeletal muscle effects of starvation and insulin. Effects of 3 days of starvation on catabolism of leucine and .alpha.-ketoisocaproic acid in skeletal muscle were examined using a perfused hindquarter preparation. The perfusate contained 0.2 mM [1-14C]- or [U-14C]leucine, all other amino acids at...

Helland S.J.; Trenkle A.; Nissen S.; Ewan R.C., 1984: Effects of dietary glucose and sucrose on whole body and hind limb metabolism of leucine and alpha keto iso caproate in vivo. Federation Proceedings 43(3): ABSTRACT 1042

Matthews D.E.; Schwarz H.P.; Yang R.D.; Motil K.J.; Young V.R.; Bier D.M., 1982: Relationship of plasma leucine and alpha keto iso caproate during a l 1 carbon 13 labeled leucine infusion in man a method for measuring human intra cellular leucine tracer enrichment. The keto analog of leucine, .alpha.-ketoisocaproate (KIC), is formed intracellularly from leucine and is released, in part, into the systemic circulation. KIC can be used to estimate intracellular leucine tracer enrichment in man during labeled-le...

Noda C.; Ichihara A., 1974: Control of ketogenesis from amino acids part 2 ketone bodies formation from alpha keto iso caproate the keto analog of leucine by rat liver mitochondria. Journal of Biochemistry (Tokyo) 76(5): 1123-1130

Teigland M.; Klungsoyr L., 1983: Accumulation of alpha keto iso caproate from leucine in homogenates of tissues from rainbow trout salmo gairdneri and rat an improved method for determination of branched chain keto acids. The dinitrophenyl hydrazone method for determination of branched chain keto acids was improved by the inclusion of a chromatographic purification step. The dinitrophenyl hydrazone of the keto acid was purified by high-pressure liquid chromatograph...

Mitch W.E.; Walser M.; Sapir D.G., 1981: Nitrogen sparing induced by leucine compared with that induced by its keto analog alpha keto iso caproate in fasting obese man. The effects of 7 consecutive daily infusions of .alpha.-ketoisocaproate (the .alpha.-keto analog of leucine) or leucine itself on urinary urea and total N excretion was measured during fasting. Two study protocols were undertaken. In protocol I su...

Hutson, S.M.; Zapalowski, C.; Cree, T.C.; Harper, A.E., 1980: Regulation of leucine and alpha-ketoisocaproic acid metabolism in skeletal muscle. Effects of starvation and insulin. Effects of 3 days of starvation on catabolism of leucine and .alpha.-ketoisocaproic acid in skeletal muscle were examined using a perfused hindquarter preparation. The perfusate contained 0.2 mM [1-14C]- or [U-14C]leucine, all other amino acids at...

Nissen S.L.; Miles J.; Haymond M.W., 1980: Effects of fasting on leucine and alpha keto iso caproate flux and inter conversion in dogs. Clinical Research 28(2): 401A

Aftring, R.P.; Block, K.P.; Buse, M.G., 1986: Leucine and isoleucine activate skeletal muscle branched-chain alpha-keto acid dehydrogenase in vivo. The response of rat skeletal muscle branched-chain alpha-keto acid dehydrogenase to administration of branched-chain amino acids in vivo was determined using a soluble preparation of the enzyme. After detergent extraction of the complex in the pre...

Williamson J.R.; Walajtys Rode E.I.; Tutwiler G., 1978: Metabolism of alpha keto iso caproate in hepatocytes from starved rats. Federation Proceedings 37(6): 1715