Selective inactivation of peroxisomal and cytosolic 3-ketothiolase IB by 2-chloro-6-phenylhexanoate in intact hepatocytes.
Rat liver mitochondria and cytosol contain two types of 3-ketothiolases, namely 3-ketothiolases IA and IB, which cleave 3-ketoacyl-coenzyme A (CoA) esters containing four or more carbons and 3-ketothiolases IIA and IIB, which cleave 3-ketoacyl-CoA esters containing four carbons, i.e. acetoacetyl-CoA (Aragon, J.J., and Lowenstein, J.M. (1983) J. Biol. Chem. 258, 4725-4733). We now report that rat liver peroxisomes also contain 3-ketothiolases IA and IB and show that incubation of hepatocytes with 2-chloro-6-phenylhexanoate causes the selective inactivation of peroxisomal and cytosolic 3-ketothiolase IB, while mitochondrial 3-ketothiolases are not appreciably affected. The basis of the selectivity of the inhibitor for peroxisomal and cytosolic 3-ketothiolases can be accounted for in terms of the specificities of the enzymes in the different pathways of beta-oxidation. Evidence is presented that 2-chloro-6-phenylhexanoate is metabolized to 2-chloro-3-keto-6-phenylhexanoyl-CoA, which then alkylates 3-ketothiolase and thereby inactivates the enzyme. Evidence is presented which suggests that cytosolic 3-ketothiolases IA and IB are not artifacts of homogenization and organelle preparation.
Sephton
G B
GB
Graduate Department of Biochemistry, Brandeis University, Waltham, Massachusetts 02254-9110.
Lowenstein
J M
JM
D000102:Acetyl-CoA C-Acyltransferase / Q000037:antagonists & inhibitors*; D000214:Acyl Coenzyme A / Q000378:metabolism; D000217:Acyltransferases / Q000037:antagonists & inhibitors*; D000478:Alkylation; D000818:Animals; D002208:Caproates / Q000378:metabolism / Q000494:pharmacology*; D003065:Coenzyme A / Q000378:metabolism; D003600:Cytosol / Q000201:enzymology*; D007700:Kinetics; D008099:Liver / Q000201:enzymology / Q000648:ultrastructure*; D008297:Male; D008830:Microbodies / Q000201:enzymology*; D008930:Mitochondria, Liver / Q000201:enzymology; D051381:Rats; D011919:Rats, Inbred Strains
D000214:Acyl Coenzyme A; D002208:Caproates; C064350:2-chloro-6-phenylhexanoate; C060151:2-bromooctanoyl-coenzyme A; D000217:Acyltransferases; D000102:Acetyl-CoA C-Acyltransferase; D003065:Coenzyme A