A new protein with nerve growth promoting activity was purified from the crude venom of theAgkistrodon halys Pallas, a Chinese snaker . Its amino-terminal sequence unexpectedly showed high homology with serine proteases, suggesting that it is a new member of the serine protease family. It also cross-reacted with antibodies against thrombin-like enzyme and possessed weak arginine esterase activity, amounting to about 3% of the activity of trypsin. However, its nerve growth promoting activity was comparable to that of nerve growth factor (NGF). It was named NGF-like protease (NLP). Northern blot analysis further demonstrated different patterns of induction of c-myc, vgfandtrkAmRNA transcription in PC12 pheochromocytoma cells treated with NGF and NLP, respectively. These data suggested that NLP represents a novel potent neurotrophic factor.