title: Conodipine-M, a novel phospholipase A2 isolated from the venom of the marine snail Conus magus.
abstract: We describe the purification and first biochemical characterization of an enzymatic activity in venom from the marine snail Conus magus. This enzyme, named conodipine-M, is a novel phospholipase A2 with a molecular mass of 13.6 kDa and is comprised of two polypeptide chains linked by one or more disulfide bonds. The amino acid sequence of conodipine-M shows little if any homology to other previously sequenced phospholipase A2 enzymes (PLA2s). Conodipine-M thus represents a new group of PLA2s. This is remarkable, since conodipine-M displays a number of properties that are similar to those of previously characterized 14-kDa PLA2s. The enzyme shows little, if any, phospholipase A1, diacyglycerol lipase, triacylglycerol lipase, or lysophospholipase activities. Conodipine-M hydrolyzes the sn-2 ester of various preparations of phospholipid only in the presence of calcium and with specific activities that are comparable to those of well known 14-kDa snake venom and pancreatic PLA2s. The Conus enzyme binds tightly to vesicles of the negatively charged phospholipid 1,2-dimyristoyl-sn-glycero-3-phosphomethanol and catalyzes the hydrolysis of this substrate in a processive fashion. Conodipine-M does not significantly discriminate against phospholipids with unsaturated versus saturated fatty acids at the sn-2 position or with different polar head groups. Linoleoyl amide and a phospholipid analog containing an alkylphosphono group at the sn-2 position are potent inhibitors of conodipine-M. We suggest that the functional resemblance of conodipine-M to other PLA2s might be explained by the utilization of similar catalytic residues.
authors.affiliation: Department of Psychiatry, University of Utah, Salt Lake City 84112.
authors.forename: J M
authors.initials: JM
authors.lastname: McIntosh
authors.forename: F
authors.initials: F
authors.lastname: Ghomashchi
authors.forename: M H
authors.initials: MH
authors.lastname: Gelb
authors.forename: D J
authors.initials: DJ
authors.lastname: Dooley
authors.forename: S J
authors.initials: SJ
authors.lastname: Stoehr
authors.forename: A B
authors.initials: AB
authors.lastname: Giordani
authors.forename: S R
authors.initials: SR
authors.lastname: Naisbitt
authors.forename: B M
authors.initials: BM
authors.lastname: Olivera
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism; D008969:Molecular Sequence Data; D008978:Mollusk Venoms / Q000201:enzymology*; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D054466:Phospholipases A1; D054467:Phospholipases A2; D054497:Phospholipases A2, Secretory; D017386:Sequence Homology, Amino Acid; D012908:Snails / Q000201:enzymology*; D013379:Substrate Specificity
chemical_list: D008978:Mollusk Venoms; D010741:Phospholipases A; D054466:Phospholipases A1; D054467:Phospholipases A2; D054497:Phospholipases A2, Secretory; C092305:conodipine M; D002118:Calcium