title: Phospholipase A2 from Trypanosoma congolense: characterization and haematological properties.
abstract: Phospholipase A2 was isolated from Trypanosoma congolense and purified to electrophoretic homogeneity. The enzyme appeared to exist in a dimeric form with subunit molecular weights of 16,500 and 18,000. It had a pH optimum of 6.8. Kinetic analysis with different substrates, showed that the enzyme had exceptional specificity for 1,2,dimyristoyl-sn-phosphatidylcholine and 1,2,dioleoyl-sn-phosphatidylcholine with Km values of 1.85 x 10(-3) M and 2.12 x 10(-3) M respectively. The Arrhenius plot was linear with an activation energy of 5.8 kcal mol-1. Inhibition studies with parahydroxy-mercuribenzoate and tributyl-tin-oxide were positive thus implicating a thiol group at the catalytic site of the enzyme. The enzyme was stable to heat treatment and possessed haemolytic and anticoagulating properties.
authors.affiliation: Department of Biochemistry, Ahmadu Bello University, Zaria, Nigeria.
authors.forename: A J
authors.initials: AJ
authors.lastname: Nok
authors.forename: K A
authors.initials: KA
authors.lastname: Esievo
authors.forename: S
authors.initials: S
authors.lastname: Ibrahim
authors.forename: A I
authors.initials: AI
authors.lastname: Ukoha
authors.forename: C O
authors.initials: CO
authors.lastname: Ikediobi
mesh_terms: D000818:Animals; D001777:Blood Coagulation / Q000502:physiology*; D002417:Cattle; D004134:Dimyristoylphosphatidylcholine / Q000378:metabolism; D006168:Guinea Pigs; D006801:Humans; D010314:Partial Thromboplastin Time; D010713:Phosphatidylcholines / Q000378:metabolism; D010741:Phospholipases A / Q000302:isolation & purification / Q000378:metabolism*; D054467:Phospholipases A2; D051381:Rats; D013379:Substrate Specificity; D014348:Trypanosoma congolense / Q000201:enzymology*
chemical_list: D010713:Phosphatidylcholines; D010741:Phospholipases A; D054467:Phospholipases A2; C017251:1,2-oleoylphosphatidylcholine; D004134:Dimyristoylphosphatidylcholine