Characterization of two arginine ester hydrolases from Mojave rattlesnake (Crotalus scutulatus scutulatus) venom.

Two arginine ester hydrolases, designated AAEI and AAEII, from the venom of Crotalus scutulatus scutulatus have been investigated. The amino acid content of both enzymes were very similar and both esterases contained carbohydrate. Following treatment of AAEI and AAEII with neuraminidase, both enzymes migrated identically in two electrophoresis systems and one electrofocusing system. The esterase activities of both enzymes were optimally active in the range pH 8.0-8.5. Neither esterase hydrolyzed casein, hemoglobin (Hb) or alpha-N-benzoyl-DL-arginine-p-nitroaniline (BAPNA), yet both AAEI and AAEII hydrolyzed alpha-N-benzoyl-L-arginine ethyl ester (BAEE), alpha-N-benzoyl-L-arginine methyl ester (BAME), p-tosyl-L-arginine methyl ester (TAME) and acetylphenylalanylarginine methyl ester (Ac-Phe-Arg-OMe). The esterase activities of the two enzymes were inhibited by serine specific reagents and benzamide, but not by EDTA or soybean trypsin inhibitor. The Km values for each enzyme with alpha-N-benzoyl-L-arginine ethyl ester and acetylphenylalanylarginine methyl ester were determined. Neither esterase displayed thrombin-like or fibrinolytic activities. Both AAEI and AEII possessed kinin releasing activity as shown by the twitch response of an isolated rat uterus. The N-terminal sequences of AAEI and AAEII were identical and both enzymes sequences were similar to other arginine esterases from crotalid venoms. The properties of AAEI and AAEII are compared to several other arginine esterases possessing kallikrein-like activities which have been isolated from snake venoms.