We purified pancreatic deoxyribonucleases I (DNases I) from three snakes, Elaphe quadrivirgata, Elaphe climaco-phoraandAgkistrodon blomhoffii, and cloned their cDNAs. Each mature snake DNase I protein comprised 262 amino acids. Wild-type snake DNases I with Leu130 were more thermally unstable than wild-type mammalian and avian DNases I with Ile130. After substitution of Leu130Ile, the thermal stabilities of the snake enzymes were higher than those of their wild-type counterparts and similar to mam-malian wild-type enzyme levels
