7S NGF alpha chain stabilizes the 7S complex. The beta dimer promotes neurite growth. The gamma chain is an arginine-specific protease; it may also have plasminogen activator activity, as well as mitogenic activity for chick embryo fibroblasts. Preferential cleavage of Arg-|-Xaa bonds in small molecule substrates. Highly selective action to release kallidin (lysyl-bradykinin) from kininogen involves hydrolysis of Met-|-Xaa or Leu-|-Xaa. Binds 2 Zn(2+) ions per 7S complex. The Zn(2+) ions are bound at the alpha-gamma interfaces. 7S nerve growth factor is composed of two alpha chains, a beta dimer composed of identical chains, and two gamma chains. This precursor is cleaved into segments to produce the active form of the gamma chain, which occurs naturally as combinations of either two or three segments held together by disulfide bonds: B1 and A, or B1, C and B2. Belongs to the peptidase S1 family. Kallikrein subfamily.