An essential arginine residue in porcine phospholipiase A2.
Reaction of phenylglyoxal, a reagent specific for arginine residues, with porcine phospholipiase A2 results in complete elimination of catalytic activity. The modification reaction is markedly dependent on pH. Other dicarbonyl compounds such as 2,3-butanedione and 1,2-cyclohexanedione also react with the enzyme to cause loss of activity but at significantly slower rates. At pH 7.0, the inactivation can be slightly retarded in the presence of Ca2+ and almost completely prevented in the  presence of n-alkylphosphorylchline inhibitors. At pH 8.5, the n-alkylphosphorylcholine inhibitors are less effective. The decrease in enzymatic activity correlates with the modification of about 1 arginine residue/phospholipase A2 molecule. The data suggest that the arginine is involved in the binding of the phosphate portion of the substrate to the enzyme.
D000447:Aldehydes / Q000494:pharmacology*; D000818:Animals; D001120:Arginine; D001665:Binding Sites; D002118:Calcium / Q000494:pharmacology; D003512:Cyclohexanones / Q000494:pharmacology; D003931:Diacetyl / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010179:Pancreas / Q000201:enzymology; D010658:Phenylglyoxal / Q000494:pharmacology*; D010713:Phosphatidylcholines / Q000494:pharmacology; D010740:Phospholipases / Q000378:metabolism*; D010741:Phospholipases A / Q000378:metabolism*; D011485:Protein Binding; D013329:Structure-Activity Relationship; D013552:Swine
C026150:1,2-dicyclohexanedione; D000447:Aldehydes; D003512:Cyclohexanones; D010713:Phosphatidylcholines; D001120:Arginine; D010740:Phospholipases; D010741:Phospholipases A; D003931:Diacetyl; D010658:Phenylglyoxal; D002118:Calcium