Acetate generation in rat liver mitochondria; acetyl-CoA hydrolase activity is demonstrated by 3-ketoacyl-CoA thiolase.
Acetate has been found as an endogenous metabolite of beta-oxidation of fatty acids in liver. In order to investigate the regulation of acetate generation in liver mitochondria, we attempted to purify a mitochondrial acetyl-CoA hydrolase in rat liver. This acetyl-CoA-hydrolyzing activity in isolated mitochondria was induced by the treatment of rats with di(2-ehtylhexyl)phthalate (DEHP), a peroxisome proliferator which induces expression of several peroxisomal and mitochondrial enzymes involved in beta-oxidation of fatty acids. The purified enzyme was 43-kDa in molecular mass by SDS/PAGE. Internal amino acid sequencing of this enzyme revealed that it was identical with mitochondrial 3-ketoacyl-CoA thiolase, suggesting that this enzyme has two kinds of activities, 3-ketoacyl-CoA thiolase and acetyl-CoA hydrolase activities. Kinetic studies clearly indicated that this enzyme had the both activities and each activity was inhibited by the substrates of the other activity, that is, 3-ketoacyl-CoA thiolase activity was inhibited by acetyl-CoA, on the other hand, acetyl-CoA hydrolase activity was inhibited by acetoacetyl-CoA in a competitive manner. These findings suggested that acetate generation in liver mitochondria is a side reaction of this known enzyme, 3-ketoacyl-CoA thiolase, and this enzyme may regulate its activities depending on each substrate level.
Yamashita
Hiromi
H
Department of Nutritional Science, Faculty of Health and Welfare Science, Okayama Prefectural University, 111 Kuboki, Soja-shi, Okayama 719-1197, Japan. yamashit@fhw.oka-pu.ac.jp
Itsuki
Ai
A
Kimoto
Masumi
M
Hiemori
Miki
M
Tsuji
Hideaki
H
D000085:Acetates / Q000378:metabolism*; D000102:Acetyl-CoA C-Acyltransferase / Q000378:metabolism*; D000104:Acetyl-CoA Hydrolase / Q000302:isolation & purification / Q000378:metabolism*; D000214:Acyl Coenzyme A / Q000378:metabolism; D000818:Animals; D002850:Chromatography, Gel; D004051:Diethylhexyl Phthalate / Q000494:pharmacology; D004789:Enzyme Activation; D007700:Kinetics; D008297:Male; D008930:Mitochondria, Liver / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
D000085:Acetates; D000214:Acyl Coenzyme A; D004051:Diethylhexyl Phthalate; D000102:Acetyl-CoA C-Acyltransferase; D000104:Acetyl-CoA Hydrolase