Evidence for two separate beta-ketoacyl CoA reductase components of the hepatic microsomal fatty acid chain elongation system in the rat.
The hepatic microsomal fatty acid chain elongation system can utilize either NADPH or NADH. Elongation activity, measured as the rate of malonyl CoA incorporation into palmitoyl CoA, was enhanced by a fat-free diet and by bovine serum albumin (BSA) when either cofactor was employed. When the intermediate products were determined, it was observed that in the presence of BSA and NADPH, the predominant product was the saturated elongated fatty acid, whereas in the presence of BSA and NADH, the major intermediate was the beta-ketoacyl derivative. Employing beta-ketostearoyl CoA as substrate, BSA markedly inhibited NADH-supported beta-ketoacyl CoA reductase activity and stimulated NADPH-supported activity. Furthermore, the sum of the NADH-dependent and NADPH-dependent beta-ketoreductase activities approximated the activity obtained when both cofactors were present in the incubation medium, suggesting the existence of two beta-ketoacyl CoA reductases, one using NADH and the other, NADPH.
Nagi
M N
MN
Department of Pharmacology, University of Connecticut Health Center, Farmington 06032.
Cook
L
L
Suneja
S K
SK
Peluso
P S
PS
Laguna
J C
JC
Osei
P
P
Cinti
D L
DL
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000429:Alcohol Oxidoreductases / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D015152:Blotting, Northern; D015139:Blotting, Southern; D002460:Cell Line; D064429:Fatty Acid Synthases / Q000235:genetics*; D005434:Flow Cytometry; D015870:Gene Expression; D005796:Genes; D006801:Humans; D015151:Immunoblotting; D007527:Isoenzymes / Q000235:genetics* / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics; D008862:Microsomes, Liver / Q000201:enzymology*; D051381:Rats; D012710:Serum Albumin, Bovine / Q000494:pharmacology
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D007527:Isoenzymes; D008562:Membrane Glycoproteins; D012710:Serum Albumin, Bovine; D000429:Alcohol Oxidoreductases; C023744:acetoacetyl-CoA reductase; D064429:Fatty Acid Synthases