title: Inhibition of Clostridium perfringens phospholipase C by ammonium and sulfonium dications.
abstract: Polyamines, alkyldiammonium and alkyldisulfonium salts, inhibit the Clostridium perfringens phospholipase C-catalyzed hydrolysis of 1-S-phosphocholine-2-O-hexadecanoyl-1-mercapto-2-ethanol (1) at pH 7.5, 37 degrees C, mu = 1.0 with KCl. Simple saturation kinetics are observed as both 1 and [Ca2+] are varied and simple linear inhibition is observed. The data are consistent with a non-competitive mechanism that involves binding of the inhibitors to free enzyme, E.[Ca2+] and E.[Ca2+].[S]; the inhibition constants for decamethylenebis(trimethylammonium) and decamethylenebis(dimethylsulfonium) bromides are 90 and 0.28 mM, respectively. It is suggested that the enhanced inhibition by the alkyldisulfonium salts results from more favorable equilibrium constants for contact ion-pair formation or from the formation of tetracoordinate sulfuranes.
authors.affiliation: Department of Chemistry, University of Illinois, Chicago 60680.
authors.forename: P R
authors.initials: PR
authors.lastname: Young
authors.forename: W R
authors.initials: WR
authors.lastname: Synder
authors.forename: R F
authors.initials: RF
authors.lastname: McMahon
mesh_terms: D000641:Ammonia / Q000494:pharmacology*; D002413:Cations, Divalent; D003016:Clostridium perfringens / Q000201:enzymology*; D005227:Fatty Acids / Q000378:metabolism; D006868:Hydrolysis; D007700:Kinetics; D010767:Phosphorylcholine / Q000378:metabolism; D011073:Polyamines / Q000494:pharmacology; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology*; D013452:Sulfonium Compounds / Q000494:pharmacology*; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors*
chemical_list: D002413:Cations, Divalent; D005227:Fatty Acids; D011073:Polyamines; D000644:Quaternary Ammonium Compounds; D013452:Sulfonium Compounds; D010767:Phosphorylcholine; C073834:1-S-phosphocholine-2-O-hexadecanoyl-1-mercapto-2-ethanol; D000641:Ammonia; D010738:Type C Phospholipases