SUBUNIT INTERACTION AND ENZYMATIC ACTIVITY OF MOUSE 7S NERVE GROWTH FACTOR

The 7S nerve growth factor preparation possesses a potent esterase activity on the substrate α-A-benzoyl-L-arginine ethyl ester. Upon dissociation of the parent molecule, this enzymatic activity is carried by the γ subunits alone. The 7S material differs from the isolated γ subunits when tested at neutral pH in that it exhibits an initial lag phase during substrate hydrolysis and expresses an enzymatic activity lower than would be expected by the stoichiometric contribution of the γ subunits to the 7S complex. The lowered activity is shown to be the result of a specific combination of the α and β subunits with the γ subunits to form the 7S species. The lag phase is shown to be generated by dilution of the 7S preparation for enzymatic assay and may be eliminated by preincubation of this material at low concentrations. A model is presented in which an active form of the γ subunit is released in dissociation-equilibrium with the enzymatically inactive, or very poorly active, parent 7S species. This hypothesis is supported by the effects produced on the observed enzymatic activity of the 7S complex by a number of different manipulations of the assay conditions. © 1969, American Chemical Society. All rights reserved.