Palmitoyl-CoA elongation in brain microsomes: dependence on cytochrome b5 and NADH-cytochrome b5 reductase.
Experiments were performed to demonstrate the involvement of electron transport system in fatty acid elongation in rat brain microsomes. Mercuric chloride and p-chloromercuriphenylsulfonate, inhibitors on NADH-cytochrome b5 reductase, at 32 microM inhibited NADH-supported palmitoyl-CoA elongation to 30 and 60% of control activity, respectively, whereas NADPH-supported palmitoyl-CoA elongation was unaffected by these mercurials. An antibody to rat liver NADH-cytochrome b5 reductase inhibited brain microsomal NADH-cytochrome b5 reductase activity and NADH-dependent palmitoyl-CoA elongation. Treatment of brain microsomes with trypsin diminished the cytochrome b5 content; NADH- and NADPH-cytochrome c reductase activities were significantly decreased, but the decrease in NADH-cytochrome b5 reductase activity was relatively small. Whereas essentially no incorporation of malonyl-CoA into palmitoyl-CoA was observed with trypsin-treated microsomes, addition of detergent-solubilized cytochrome b5 resulted in a recovery of fatty acid elongation. These results indicate the presence of an electron transport system, NADH-NADH-cytochrome b5 reductase-cytochrome b5-fatty acid elongation, in brain microsomes.
D002731:4-Chloromercuribenzenesulfonate / Q000494:pharmacology; D000214:Acyl Coenzyme A / Q000378:metabolism*; D000818:Animals; D000906:Antibodies; D001921:Brain / Q000378:metabolism*; D003579:Cytochrome Reductases / Q000302:isolation & purification / Q000378:metabolism*; D003573:Cytochrome b Group / Q000302:isolation & purification / Q000378:metabolism*; D042966:Cytochrome-B(5) Reductase; D015786:Cytochromes b5; D005260:Female; D007700:Kinetics; D008247:Lysosomes / Q000201:enzymology; D008297:Male; D008627:Mercuric Chloride / Q000494:pharmacology; D008861:Microsomes / Q000378:metabolism*; D010171:Palmitoyl Coenzyme A / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D014357:Trypsin
D000214:Acyl Coenzyme A; D000906:Antibodies; D003573:Cytochrome b Group; D010171:Palmitoyl Coenzyme A; D008627:Mercuric Chloride; D002731:4-Chloromercuribenzenesulfonate; D015786:Cytochromes b5; D003579:Cytochrome Reductases; D042966:Cytochrome-B(5) Reductase; D014357:Trypsin