Purification and characterization of a novel phospholipase A2 from king cobra (Ophiophagus hannah) venom |
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Authors: | Jen-Yirng Chiou Long-Sen Chang Lyn-Nou Chen Chun-Chang Chang |
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Affiliation: | (1) Department of Biochemistry, Kaohsiung Medical College, Kaohsiung, Taiwan 807, ROC |
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Abstract: | A novel phospholipase A2, designated as Oh-DE-2, was isolated from the venom ofOphiophagus hannah (king cobra) by successive chromatography on SP-Sephadex C-25, DE-52, and Q-Sepharose columns. Oh-DE-2 with pI 5.1 showed an apparent molecular weight of 14 kD as revealed by SDS-PAGE and gel filtration. The amino acid sequence was homologous with those of PLA2s from Elapidae venoms. Oh-DE-2 was effectively inactivated byp-bromophenacyl bromide, indicating that the conserved His-48 is essential for its enzymatic activity. However, modification of the conserved Trp-19 did not cause a precipitous drop in the enzymatic activity of Oh-DE-2 as observed with PLA2s fromNaja naja atra andBungarus multicinctus venoms. A quenching study showed that the microenvironment of Trp in Oh-DE-2 was inaccessible to acrylamide, iodide, or cesium, a finding which was different from those observed with PLA2s fromN. naja atra andB. multicinctus venoms. These results might suggest that, unlike other PLA2 enzymes, Trp-19 in Oh-DE-2 is not directly involved in its enzymatic mechanisms. |
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Keywords: | King cobra phospholipase A2 histidine modification tryptophan modification fluorescence quenching |
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