Do rat kidney cortex microsomes possess the enzymatic machinery to desaturate and chain elongate fatty acyl-CoA derivatives?
Rat kidney cortex microsomal preparations were unable to catalyze delta 9, delta 6 and delta 5 desaturation of stearoyl-coenzyme A (CoA), linoleoyl-CoA and dihomo-gamma-linolenoyl-CoA, respectively. The kidney cortex microsomal fraction, however, did catalyze the malonyl-CoA dependent fatty acyl-CoA elongation. The biochemical properties of palmitoyl-CoA elongation were studied as a function of protein concentration, time, reduced nicotinamide adenine dinucleotide phosphate (NADPH), malonyl-CoA and substrate concentrations; of the substrates investigated, delta 6,9,12-18:3 was the most active. Unlike what was observed in the hepatic system, a high-carbohydrate, fat-free diet did not induce kidney fatty acid chain elongation. All intermediate kidney cortex microsomal reactions, i.e., beta-ketoacyl-CoA reductase, beta-hydroxyacyl-CoA dehydrase and trans-2-enoyl-CoA reductase activities, were significantly higher (greater than one order of magnitude) than the condensing enzyme activity, suggesting that the rate-limiting step in total elongation is the initial condensation reaction. Contrary to other reports, the results suggest that the kidney cannot synthesize arachidonic acid needed for eicosanoid production.
Suneja
S K
SK
Department of Pharmacology, University of Connecticut Health Center, Farmington 06030.
Nagi
M N
MN
Cook
L
L
Osei
P
P
Cinti
D L
DL
D000214:Acyl Coenzyme A / Q000378:metabolism*; D000429:Alcohol Oxidoreductases / Q000378:metabolism*; D000818:Animals; D004746:Enoyl-CoA Hydratase / Q000378:metabolism*; D044943:Fatty Acid Desaturases / Q000378:metabolism*; D007672:Kidney Cortex / Q000201:enzymology*; D007700:Kinetics; D008297:Male; D008861:Microsomes / Q000201:enzymology*; D051381:Rats; D011919:Rats, Inbred Strains; D013379:Substrate Specificity
D000214:Acyl Coenzyme A; D000429:Alcohol Oxidoreductases; C023744:acetoacetyl-CoA reductase; D044943:Fatty Acid Desaturases; D004746:Enoyl-CoA Hydratase