The regulation of fatty acid chain elongation in rat liver microsomes: role of fasting and CoASH.
The elongation system for palmitic acid in rat liver microsomes was decreased to 1/3 by fasting, while the elongation of eicosapentaenoic acid was not sensitive to fasting. The rate of eicosapentaenoic acid elongation in the fed state was 50% higher than using palmitic acid as a substrate. The saturated and polyunsaturated fatty acyl-CoA substrates exhibited positive cooperativity on the rate-limiting condensing step in the elongation system, with a Hill constant of approx. 2. An inhibition by CoASH on the total elongation reaction as well as on the condensation step was demonstrated using acyl-CoA substrates, and followed a hyperbolic pattern. The concentrations giving a 50% inhibition (30-70 microM) were in the range found in rat hepatocyte cytosol, indicating that free CoASH has the potential to act as a physiological regulator.
Reichelt
W H
WH
Institute for Nutrition Research, University of Oslo, Norway.
Grav
H J
HJ
Christiansen
E N
EN
D000818:Animals; D003065:Coenzyme A / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology; D015118:Eicosapentaenoic Acid / Q000378:metabolism; D005215:Fasting; D005227:Fatty Acids / Q000737:chemistry / Q000378:metabolism*; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology / Q000378:metabolism*; D019308:Palmitic Acid; D010169:Palmitic Acids / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
D005227:Fatty Acids; D010169:Palmitic Acids; D019308:Palmitic Acid; D015118:Eicosapentaenoic Acid; D003065:Coenzyme A