Comparison of enzyme kinetics and inhibition of three North American snake venoms

Baseline gelatinase activities of venom from three snake species: Agkistrodon contortrix contortrix (Acc), Crotalus atrox (C. atrox) and Cerastes cerastes (Ccc), were measured using EnzChek® Gelatinase/Collagenase Kit E12055, and found to be similar between Acc and Ccc, while C. atrox venom showed lower baseline activity compared to the other two. Based on Selwyn plots of experimental data, venom from Acc and C. atrox demonstrate enzymatic stability over a wide range of substrate concentrations and reaction times, while Ccc venom demonstrated lower levels of stability under the same conditions. It was also found that the protease inhibitor NNGH inhibits the gelatinase activity of C. atrox venom more than it does for Acc venom. The inhibitory effect on venom gelatinase activity is not affected by enzyme pretreatment with NNGH prior to the gelatinase reaction. The DMSO used in the reaction also has an inhibitory effect, which is greater for C. atrox than for Acc. These results will be useful in understanding reaction kinetics of snake venom enzyme inhibition, which could lead to alternative treatment modalities for envenomation.