Transamination and oxidative decarboxylation of L-isoleucine, L-alloisoleucine and related 2-oxo acids in perfused rat hind limb muscle.
Metabolism of L-isoleucine, L-alloisoleucine and corresponding 2-oxo acids in rat hind limb muscle was comparatively studied under steady-state perfusion conditions. At 0.5 mM L-[1-14C]isoleucine, apparent transamination and 2-oxo acid decarboxylation rates amounted to about 17 and 4 nmol/min per g of muscle, respectively. With L-allo[1-14C]isoleucine, the corresponding rates were about 5- and 10-fold lower, respectively. After addition of dichloroacetate (1-5 mM), the portion of (S)- and (R)-methyl-2-oxopentanoate undergoing further oxidative decarboxylation within the tissue was similarly increased by over 40%. In perfusions with 0.5 mM (R,S)-3-methyl-2-oxopentanoate and tracer doses of 1-14C-labeled (S)- or (R)-enantiomer, the 14CO2 production was comparable (about 0.5 nmol/min per g of muscle). Dichloroacetate caused a several-fold increase in 14CO2 release from either enantiomer, apparent 2-oxo acid transamination rates remaining unaffected. Indications for a racemization of 2-oxo acid were not obtained in the experiments. The results are discussed with respect to the appearance/disappearance of L-alloisoleucine in vivo and to the fact that (R)-3-methyl-2-oxopentanoate, but not L-alloisoleucine, can support growth of rats on a diet deficient in L-isoleucine.
Schadewaldt
P
P
Institut für Physiologische Chemie II, Universität Düsseldorf, F.R.G.
Radeck
W
W
Hammen
H W
HW
Staib
W
W
D000409:Alanine / Q000378:metabolism; D000586:Amination; D000597:Amino Acids, Branched-Chain / Q000378:metabolism; D000818:Animals; D003653:Decarboxylation; D003999:Dichloroacetic Acid / Q000494:pharmacology; D005971:Glutamates / Q000378:metabolism; D018698:Glutamic Acid; D005973:Glutamine / Q000378:metabolism; D066298:In Vitro Techniques; D007532:Isoleucine / Q000378:metabolism*; D008297:Male; D009132:Muscles / Q000378:metabolism*; D010084:Oxidation-Reduction; D010649:Phenylalanine / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013237:Stereoisomerism
D000597:Amino Acids, Branched-Chain; D005971:Glutamates; D007532:Isoleucine; D005973:Glutamine; D018698:Glutamic Acid; D010649:Phenylalanine; D003999:Dichloroacetic Acid; D000409:Alanine