Nerve growth factor is a target-derived neurotrophic factor acting on sympathetic and neural crest-derived sensory neurons in the peripheral nervous system (PNS) and some populations of cholinergic neurons in the central nervous system (CNS; Levi-Montalcini and Hamburger, 1951; 1953; Levi-Montalcini, 1987; Hefti and Weiner, 1986; Thoenen and Barde, 1980). Nerve growth factor isolated from mouse submaxillary glands has a sedimentation coefficient of 7S which lacks biological activity (Varon et al.,1972; Stach and Shooter, 1980) and is made up of two alphas, one beta, and two gamma subunits (α₂βγ₂). The biologically active form is the β-subunit, a homodimer made up of two identical polypeptides. Each chain contains three intrachain disulfide bonds which are crucial for biological activity since the reduction of these bonds abolishes biological activity (Greene and Shooter, 1980; Perez-Polo et al., 1990; Fahnestock, 1991). There are significant homologies in the amino acid sequence of the α -and γ-subunits (Greene et al.,1969; Thomas et al., 1981; Evans and Richards, 1985). The γ-subunit of 7S NGF (γ-NGF) is an arginine- or lysine-specific trypsin-like serine proteinase in the kallikrein gene family (Thomas et al., 1981; Evans and Richards, 1985; Evans et al., 1987). The γ-NGF has been postulated to function during the processing of the β-NGF precursor and may participate in cellular migration or tissue remodeling. The γ-NGF can also cleave recombinant single chain urokinase-type plasminogen activators which might be involved in cellular migration by activating a proteinase cascade (Wolf et al.,1993).The α-subunit also belongs to the kallikrein gene family (Evans and Richards, 1985). Although α-NGF may protect β-NGF from proteolytic degradation or inhibit NGF biological activity via formation of the 7S complex, a definitive biological function for the α-subunit has not been established.