Methionine metabolism by rat muscle and other tissues. Occurrence of a new carnitine intermediate.
Perfused rat hindquarter preparations were shown to incorporate radioactivity from [U-14C]methionine into citrate-cycle intermediates, lactate, alanine, glutamate, glutamine and CO2. During perfusion, large amounts of methionine were also oxidized to methionine sulphoxide. The capacity for transamination of methionine or its oxo analogue, 4-methylthio-2-oxobutyrate, by muscle extracts was demonstrated. Rat skeletal muscle, heart, liver and kidney mitochondria, when incubated with the latter plus radiolabelled carnitine, formed a newly identified carnitine derivative, 3-methylthiopropionylcarnitine. It is concluded that the capacity for oxidation of methionine by a trans-sulphuration-independent pathway occurs in several mammalian tissues. The extent of inter-organ handling of intermediates in this pathway(s) is discussed.
Department of Biochemistry, Indiana University School of Medicine, Indianapolis 46223.
P W
PW
Scislowski
B M
BM
Hokland
W I
WI
Davis-van Thienen
J
J
Bremer
E J
EJ
Davis
D000217:Acyltransferases / Q000378:metabolism; D000818:Animals; D002331:Carnitine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000378:metabolism; D002855:Chromatography, Thin Layer; D002952:Citric Acid Cycle; D008297:Male; D008715:Methionine / Q000031:analogs & derivatives / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism; D009132:Muscles / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D014018:Tissue Distribution; D000637:Transaminases / Q000378:metabolism
C054316:methylthiopropionylcarnitine; C014632:2-keto-4-methylthiobutyric acid; D008715:Methionine; D000217:Acyltransferases; C019181:glutamine phenylacetyltransferase; D000637:Transaminases; D002331:Carnitine