Arginyl residues are involved in acyl-CoA binding to the elongase from etiolated leek seedlings.
The C18:0-CoA elongase from etiolated leek seedling microsomes was inactivated by treatment with phenylglyoxal, a reagent which specifically modifies arginyl residues. In the presence of 20 mM phenylglyoxal, 95% of the C18:0-CoA elongation was inhibited. The condensation and dehydration reactions of the overall elongation were totally inhibited, whereas enoyl-CoA reductase activity was diminished by 75%, but the nature of the final elongation product was unchanged. Phenylglyoxal did not modify the C18:0-CoA partition between membrane and aqueous compartments; moreover, [1-14C]phenylglyoxal labeling experiments showed a covalent binding of the inhibitor to membrane proteins. The ability of several substrates to prevent the inactivation by phenylglyoxal was investigated. NADH and NADPH had no effect. CoA led to a 75% protection, and the incorporation of [14C]phenylglyoxal was strongly affected by 10 mM CoA. The acyl chain length of the acyl-CoAs played also a crucial role in preventing the binding of phenylglyoxal. The maximal prevention of phenylglyoxal inhibition was obtained with C18:0-CoA. This suggests that arginyl residues could be present in the vicinity of the acyl-CoA binding site of the subunits of C18:0-CoA elongase.
Santarelli
X
X
ESTBB Université Victor Segalen Bordeaux 2, 146 Rue Léo Saignat, 33076 Bordeaux Cédex, France.
Chevalier
S
S
Cassagne
C
C
Lessire
R
R
D000214:Acyl Coenzyme A / Q000378:metabolism*; D051080:Acyl-Carrier Protein S-Malonyltransferase; D000217:Acyltransferases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D001120:Arginine / Q000378:metabolism* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D007700:Kinetics; D008316:Malonyl Coenzyme A / Q000378:metabolism; D008861:Microsomes / Q000201:enzymology; D009243:NAD / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D019697:Onions; D010658:Phenylglyoxal / Q000494:pharmacology; D010944:Plants / Q000201:enzymology; D013379:Substrate Specificity
D000214:Acyl Coenzyme A; D009243:NAD; C017725:stearoyl-coenzyme A; D008316:Malonyl Coenzyme A; D009249:NADP; D001120:Arginine; D000217:Acyltransferases; D051080:Acyl-Carrier Protein S-Malonyltransferase; D010658:Phenylglyoxal