title: Inhibition of phospholipases by Met-Leu-Phe-Ile-Leu-Ile-Lys-Arg-Ser-Arg-His-Phe, C terminus of middle-sized tumor antigen.
abstract: The N and C terminals and tyrosine-phosphorylating site of the middle-sized tumor antigen of polyoma virus were chemically synthesized. The sequences of these peptides were Met-Asp-Arg-Val-Leu-Ser-Arg-Ala-Asp-Lys (N-MT), Met-Leu-Phe-Ile-Leu-Ile-Lys-Arg-Ser-Arg-His-Phe (C-MT), and Glu-Glu-Glu-Glu-Tyr-Met-Pro-Met-Glu (MT-Tyr), respectively. Among these peptides, the C-MT peptide inhibited phospholipase A2 (EC 3.1.1.4), phospholipase C (EC 3.1.4.3), and phospholipase D (EC 3.1.4.4). In addition, phosphatidylinositol-specific phospholipase C (EC 3.1.4.10) was also inhibited by this peptide. To study the mechanism of the inhibition, kinetic analysis was performed using phospholipase A2 from porcine pancreas. The degree of inhibition of phospholipase was dose dependent, and maximal inhibition was observed at pH 8.8. This peptide inhibited phospholipase A2 in a competitive manner for low-affinity sites of Ca2+, and in a noncompetitive manner for phospholipid substrates. When a fatty acid in the 2 position of the glycerol moiety of phosphatidylcholine was replaced by palmitic acid (C16:0), oleic acid (C18:1), linoleic acid (C18:2), eicosatrienoic acid (C20:3), or arachidonic acid (C20:4), the degree of inhibition of phosphatidylcholine hydrolysis by the C-MT peptide decreased. Inhibition of phospholipase A2 by the C-MT peptide was reversed by low concentrations of sodium deoxycholate but not by Triton X-100 or Nonidet P40, nonionic detergents. These detergents and the modification of acyl groups altered the micellar state of phospholipids. These results, taken together, suggest that the binding of the C-MT peptide near the low-affinity Ca2+ binding sites modifies the interaction of phospholipid substrates with the active center of phospholipase A2.
authors.forename: Y
authors.initials: Y
authors.lastname: Notsu
authors.forename: S
authors.initials: S
authors.lastname: Namiuchi
authors.forename: T
authors.initials: T
authors.lastname: Hattori
authors.forename: K
authors.initials: K
authors.lastname: Matsuda
authors.forename: F
authors.initials: F
authors.lastname: Hirata
mesh_terms: D000818:Animals; D000952:Antigens, Polyomavirus Transforming; D000957:Antigens, Viral, Tumor; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism; D001409:Bacillus cereus / Q000201:enzymology; D001514:Bee Venoms; D001665:Binding Sites; D002460:Cell Line; D003016:Clostridium perfringens / Q000201:enzymology; D003435:Crotalid Venoms; D003902:Detergents / Q000494:pharmacology; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007945:Leukemia, Lymphoid; D009842:Oligopeptides / Q000138:chemical synthesis / Q000494:pharmacology*; D010179:Pancreas / Q000201:enzymology; D010446:Peptide Fragments; D010740:Phospholipases / Q000037:antagonists & inhibitors*; D010741:Phospholipases A / Q000037:antagonists & inhibitors; D054467:Phospholipases A2; D010944:Plants / Q000201:enzymology; D011485:Protein Binding; D051381:Rats; D011919:Rats, Inbred Strains; D013552:Swine; D014764:Viral Proteins
chemical_list: D000952:Antigens, Polyomavirus Transforming; D000957:Antigens, Viral, Tumor; D001095:Arachidonic Acids; D001514:Bee Venoms; D003435:Crotalid Venoms; D003902:Detergents; D009842:Oligopeptides; D010446:Peptide Fragments; D014764:Viral Proteins; D016718:Arachidonic Acid; C044132:methionyl-leucyl-phenylalanyl-isoleucyl-lysyl-arginyl-seryl-arginyl-histidyl-phenylalanine; D010740:Phospholipases; D010741:Phospholipases A; D054467:Phospholipases A2