Author/Editor		Petan, Toni
Title		Nevrotoksično in encimsko delovanje modrasovih fosfolipaz A2
Type		monografija
Place		Ljubljana
Publisher		Medicinska fakulteta
Publication year		2003
Volume		str. 142
Language		slo
Abstract		Ammodytoxins (Atxs) are presynaptically neurotoxic secreted phospholipases A2 (sPLA2s) from venom of the long-nosed viper, Vipera ammodytes ammodytes. Ammodytin (Atn) I2 is a non-toxic sPLA2 from the same venom, while AtnL is a myotoxic sPLA2 homologue without enzymatic activity. Although the exact role of enzymatic activity in the process of presynaptic neurotoxicity of sPLA2s is still unknown, it has been shown that it is essential for full expression of the neurotoxic effect. In order to determine the role of different hydrophobic and aromatic residues on the interfacial binding surface (IBS) of Atxs, we prepared a number of recombinant mutant proteins of AtxA. By replacing several residues in the active site and calcium-binding loop of AtnL, we successfully prepared two enzymatically active mutants, which differed only in the substitution V31 W. By carefully analysing the enzymatic characteristics of 16 wild-type and mutant snake venom sPLA2s of group IIA (Atxs, Atns and a weakly neurotoxic sPLA2 from the Russell's viper), we searched for possible differences in the enzymatic action of neurotoxic and non-neurotoxic sPLA2s. In this study, we show that Atxs are very efficient enzymes when acting on anionic as well as on zwitterionic aggregated phospholipid substrates. Anionic phosphatidylglycerol (PG) and phosphatidylserine (PS) vesicles are very good general . substrates for Atxs. The specific enzymatic activities of our snake venom sPLA2s on vesicles composed of neutral phosphatidylcholine (PC) molecules were up to five orders of magnitude lower than that determined on anionic vesicles. The range of activities of the 16 sPLA2s on anionic PG and PS vesicles varied by up to 11- and 34-fold, respectively, while the activities on neutral PC vesicles showed a much higher variability and differed by up to 20,000-fold. (Abstract truncated at 2000 characters).
Descriptors		VIPER VENOMS PHOSPHOLIPASES A RECOMBINANT PROTEINS BINDING SITES TRANSFORMATION, GENETIC PHOSPHATIDYLCHOLINES PHOSPHATIDYLSERINES PHOSPHATIDYLGLYCEROLS VIPERIDAE CALCIUM NEUROTOXINS PLASMIDS POLYMERASE CHAIN REACTION