Functional characterization of Delta3,Delta2-enoyl-CoA isomerases from rat liver.
The degradation of unsaturated fatty acids by beta-oxidation involves Delta(3),Delta(2)-enoyl-CoA isomerases (enoyl-CoA isomerases) that catalyze 3-cis --> 2-trans and 3-trans --> 2-trans isomerizations of enoyl-CoAs and the 2,5 --> 3,5 isomerization of dienoyl-CoAs. An analysis of rat liver enoyl-CoA isomerases revealed the presence of a monofunctional enoyl-CoA isomerase (ECI) in addition to mitochondrial enoyl-CoA isomerase (MECI) in mitochondria, whereas peroxisomes contain ECI and multifunctional enzyme 1 (MFE1). Thus ECI, which previously had been described as peroxisomal enoyl-CoA isomerase, was found to be present in both peroxisomes and mitochondria. This enzyme seems to be identical with mitochondrial long-chain enoyl-CoA isomerase (Kilponen, J.M., Palosaari, P.M., and Hiltunen, J.K. 1990. Biochem. J. 269, 223-226). All three hepatic enoyl-CoA isomerases have broad chain length specificities but are distinguishable by their preferences for one of the three isomerization reactions. MECI is most active in catalyzing the 3-cis --> 2-trans isomerization; ECI has a preference for the 3-trans --> 2-trans isomerization, and MFE1 is the optimal isomerase for the 2,5 --> 3,5 isomerization. A functional characterization based on substrate specificities and total enoyl-CoA isomerase activities in rat liver leads to the conclusion that the 3-cis --> 2-trans and 2,5 --> 3,5 isomerizations in mitochondria are catalyzed overwhelmingly by MECI, whereas ECI contributes significantly to the 3-trans --> 2-trans isomerization. In peroxisomes, ECI is predicted to be the dominant enzyme for the 3-cis --> 2-trans and 3-trans --> 2-trans isomerizations of long-chain intermediates, whereas MFE1 is the key enzyme in the 2,5 --> 3,5 isomerization.
Zhang
Dongyan
D
Department of Chemistry, City College and Graduate School of the City University of New York, New York, New York 10031, USA.
Yu
Wenfeng
W
Geisbrecht
Brian V
BV
Gould
Stephen J
SJ
Sprecher
Howard
H
Schulz
Horst
H
D000818:Animals; D019748:Carbon-Carbon Double Bond Isomerases / Q000032:analysis / Q000502:physiology*; D064006:Dodecenoyl-CoA Isomerase; D008099:Liver / Q000201:enzymology* / Q000648:ultrastructure; D008297:Male; D008830:Microbodies / Q000201:enzymology; D008930:Mitochondria, Liver / Q000201:enzymology; D010084:Oxidation-Reduction; D051381:Rats; D017207:Rats, Sprague-Dawley; D013379:Substrate Specificity
D019748:Carbon-Carbon Double Bond Isomerases; D064006:Dodecenoyl-CoA Isomerase