An overview on nucleases (DNase, RNase, and phosphodiesterase) in snake venoms.

In this review, we have compiled the data on pharmacological activities associated with endogenous purine release related enzymes-nucleases (DNases, RNases, and phosphodiesterases). The results of studies on toxic effects of these enzymes, emphasizing the future directions in this field, are summarized. One of the major problems facing toxicologists is the identification and characterization of specific venom nucleases since they share similar substrate specificities and biochemical properties. In this review, we have attempted to clarify some of the discrepancies about these enzymes. Further, we have tried to correlate the existence of nuclease enzymes in relation to endogenous release of purines, a multitoxin, during snake envenomation, and we also discuss the possible actions of purines. We hope that this review will stimulate renewed interest among toxicologists to biologically characterize these enzymes and elucidate their role in envenomation.

Vanillic acid as a novel specific inhibitor of snake venom 5'-nucleotidase: a pharmacological tool in evaluating the role of the enzyme in snake envenomation.

Vanillic acid has been investigated for its inhibitory effect on Naja naja, Daboia russellii, and Trimeresurus malabaricus venom 5'-nucleotidase activity. Trimeresurus malabaricus venom 5'-nucleotidase activity was 1.3- and 8.0-fold higher than that of N. naja and D. russellii venoms, respectively. Substrate specificity studies showed that for all the venoms tested, 5'-AMP was the preferred substrate for 5'-nucleotidase. This indicates the central role of adenosine in snake envenomation. Vanillic acid selectively and specifically inhibited 5'-nucleotidase activity among several enzymes present in the three venoms tested. The inhibitor was competitive, as the inhibition was relieved by increased substrate concentration. It appears that the COOH group in vanillic acid is the determining factor for inhibition as vanillin, a structurally similar compound with respect to vanillic acid, had no inhibitory activity. This study for the first time exemplifies vanillic acid as a pharmacological tool in evaluating the role of 5'-nucleotidase in snake envenomation.