Abstract
The protein abundances of phospholipases A2 in cobra venom proteomes appear to vary among cobra species. To determine the unique distribution of snake venom phospholipases A2 (svPLA2) in the cobras, the svPLA2 activities for 15 cobra species were examined with an acidimetric and a colorimetric assay, using egg yolk suspension and 4-nitro-3-octanoyloxy benzoic acid (NOBA) as the substrate. The colorimetric assay showed significant correlation between svPLA2 enzymatic activities with the svPLA2 protein abundances in venoms. High svPLA2 activities were observed in the venoms of Asiatic spitting cobras (Naja sputatrix, Naja sumatrana) and moderate activities in Asiatic non-spitters (Naja naja, Naja atra, Naja kaouthia), African spitters (subgenus Afronaja), and forest cobra (subgenus Boulengerina). African non-spitting cobras of subgenus Uraeus (Naja haje, Naja annulifera, Naja nivea, Naja senegalensis) showed exceptionally low svPLA2 enzymatic activities. The negligible PLA2 activity in Uraeus cobra venoms implies that PLA2 may not be ubiquitous in all snake venoms. The svPLA2 in cobra envenoming varies depending on the cobra species. This may potentially influence the efficacy of cobra antivenom in specific use for venom neutralization.
Highlights
Phospholipases A2 (PLA2 ) (EC 3.1.1.4) are enzymes that hydrolyze glycerophospholipids to lysophospholipids and fatty acids
The first snake venom PLA2 enzymes were purified from the venoms of Naja naja and Naja tripudians as hemolysin due to their ability to lyse the phospholipid membranes of red blood cells [1]
2 based on two different types of PLA2 assays [37]: an acidimetric assay measured the release of proton from fatty acids during the hydrolysis of phosphate ester bond, and a that measured the release of proton from fatty acids during the hydrolysis of phosphate ester bond, colorimetric assay that measured the amount of chromogenic 4-nitro-3-hydroxybenzoic acid released and a colorimetric assay that measured the amount of chromogenic 4-nitro-3-hydroxybenzoic acid by the cleavage of PLA2 at the ester bond between the octanol group of non-micellar substrate (NOBA) [38]
Summary
Phospholipases A2 (PLA2 ) (EC 3.1.1.4) are enzymes that hydrolyze glycerophospholipids to lysophospholipids and fatty acids. The first snake venom PLA2 enzymes were purified from the venoms of Naja naja and Naja tripudians as hemolysin due to their ability to lyse the phospholipid membranes of red blood cells [1]. Homologous svPLA2 are especially abundant and diverse in the Asiatic elapids, including cobras, coral snakes, kraits, and some sea snake species [3,4,5,6], implying that the enzyme plays an essential role in the function of the venom. The snake venom PLA2 are single-chain polypeptides with 115–125 amino acid residues (13–15 kDa), and high degrees of sequence homology are observed across different cobra species [8]. SvPLA2 can differ widely in their pharmacology, contributing to the diverse toxic activities in snakebite envenoming
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