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.

Trypanocidal potentials of Azadirachta indica seeds against Trypanosoma evansi

“…Phospholipase A 2 is the enzyme that is known to trigger haemolytic anemia during the course of parasitemia (Nok et al, 1993b). The inhibition of this enzyme by NSF F3 gives an insight to how anemia can be alleviated in trypanosomiasis.…”

“…Subsequently, concentrations of the substrate were varied and an additional 100 L of 0%, 10%, 20% and 30% (w/v) of NSME were added to the reaction mixture. The activity of phospholipase A 2 was defined as the amount of enzyme required to hydrolyse 1 mg of free fatty acid from lecithin (Nok et al, 1993b).…”

The cholesterol pathway of Trypanosoma congolense could be a target for triphenyltinsalicylate and triphenylsiliconsalicylate inhibition

“…lecithin, by the release of phospholipases to release; free fatty acid and lysolecithin. 17,18 The products are then enzymatically incorporated onto the parasites. Since the acquisition of cholesterol by trypanosomes involves cell-mediated endocytosis by trypanosomal receptors, the observed TPTS/TPSS inhibition of cholesterol uptake could be due to masking of these receptors by the organometallic compounds.…”

Phospholipases A in Trypanosomatids

“…PLA 2 was isolated from T. congolense ; the enzyme appeared to exist in a dimeric form with subunit molecular weights of 16.5 and 18 kDa, had optimum pH of 6.8, and showed specificity for 1,2,dimyristoyl- sn -PC and 1,2,dioleoyl- sn -PC [55]. Inhibition studies implicated a thiol group at the catalytic site of the enzyme, which was stable to heat treatment and possessed haemolytic and anticoagulating properties [55].…”

“…Inhibition studies implicated a thiol group at the catalytic site of the enzyme, which was stable to heat treatment and possessed haemolytic and anticoagulating properties [55]. …”