ABSTRACT
Snake venom is a rich source of diverse bioactive peptides and proteins, among them enzymes, which are divided into proteinases (metallo- and serine proteinases), phospholipases A2, acetylcholinesterases, L-amino acid oxidases, hyaluronidases, nucleases and nucleotidases. Snake venom nucleases and nucleotidases belong to the least studied enzymes due to their low quantity in venoms. Many hydrolytic enzymes of snake venom interfere with different physiological processes of the prey. Hydrolytic enzymes such as nucleases (DNase, RNase and phosphodiesterase), nucleotidases (5′-nucleotidase, ATPase, ADPase and apyrase), and phosphomonoesterases (acid and alkaline phosphomonoesterases) are found in venoms of many different snakes, but their structural, patho-physiological and pharmacological properties need further study. Some of these enzymes show overlapping substrate specificities; for example, DNases, RNases and phosphodiesterases share similar properties in substrate hydrolysis but differ in their pH optima and metal ion requirement for activity. Nucleotidases such as ATPases and ADPases have overlapping substrate specificities with phosphodiesterase. However, recent proteomic/transcriptomic studies allow more distinct differentiation of these enzymes in snake venoms. These enzymes (except RNases) have high molecular masses, and all (except DNases and RNases) are metalloenzymes. The broad distribution of these enzymes in venoms suggests that they make important contributions to the patho-physiology associated with envenomation. These enzymes could possess a central role in liberating adenosine and through the action of adenosine, assist in prey immobilization. While the pharmacological properties of these enzymes are poorly characterized – mainly, effects caused by liberated adenosine are described – further research is needed to determine other pharmacological and biological activities of the enzymes. Further research is needed also for characterization of the structure–functional relationships of these snake venom enzymes.
