Comparison of the arginine esteropeptidases associated with the nerve and epidermal growth factor

The nerve growth factor (NGF) and the epidermal growth factor (EGF) of the male mouse submaxillary gland are found in association with arginine esteropeptidases. These enzymes, the gamma subunits of 7 S NGF and the EGF-binding protein, respectively, have similar molecular weights, amino acid compositions, and substrate specificities (Greene, L. A., Shooter, E. M., and Varon, S. (1969) Biochemistry 8, 3735-3741; Taylor, J.M., Mitchell, W. M., and Cohen, S. (1974) J. Biol. Chem. 249, 21-8-2194). Although on the basis of molecular weight, the EGF-binding protein has a peptide chain composition similar to that of the gamma3 subunit, it does not have the same isoelectric point nor electrophoretic properties as the subunit. In urea, its isoelectric point differs from those of the gamma1, gamma2, and gamma3 subunits. The EGF-binding protein has antigenic determinants not shared by the gamma subunits and vice versa. It also fails to replace the gamma subunits in the formation of 7 S NGF points to the specificity of this complex and supports the hypothesis that the nerve and epidermal growth factors are generated from larger precursors by the proteolytic action of their respective arginine esteropeptidases.