Cytochrome b5-dependent delta 9 desaturation of fatty acids in gastric microsomes.
Stearyl-CoA was shown to stimulate the reoxidation rate of cytochrome b5 of gastric microsomes and to decrease the reduction rate of trypsin-purified hog liver cytochrome b5 by the NADH-cytochrome b5 reductase of these microsomes. This latter effect was (1) proportional to microsome concentration and to stearyl-CoA concentration with an apparent Km of 3.3 . 10(-6) M and a Vmax of 71 nmol per min and per mg microsomal protein, (2) insensitive to ATP and inhibited by 1.4 mM KCN, (3) mimicked by palmityl-CoA but not by stearic nor palmitic acid. Direct assays carried out using [14C]stearyl- and [14C]palmityl-CoA as substrates showed a production of 0.12 nmol of oleic and palmitoleic acid, respectively, per min per mg of microsomal protein. In the presence of Tb5 antibodies the reaction was inhibited by 40%. These results support the occurrence of cytochrome b5-dependent fatty acid delta 9 desaturation in gastric microsomes.
D000214:Acyl Coenzyme A / Q000378:metabolism; D000818:Animals; D003573:Cytochrome b Group / Q000502:physiology*; D015786:Cytochromes b5; D004789:Enzyme Activation / Q000187:drug effects; D044943:Fatty Acid Desaturases / Q000378:metabolism*; D005753:Gastric Mucosa / Q000201:enzymology*; D066298:In Vitro Techniques; D008861:Microsomes / Q000201:enzymology*; D010084:Oxidation-Reduction / Q000187:drug effects; D013552:Swine
D000214:Acyl Coenzyme A; D003573:Cytochrome b Group; C017725:stearoyl-coenzyme A; D015786:Cytochromes b5; D044943:Fatty Acid Desaturases