We investigate the conversion of spin and orbital angular momentum (AM) of elliptically polarized light beams at frequencies ω 1 and ω 2, helical phase profiles, and arbitrary radial intensity distributions to AM of a signal beam at frequency resulting from four-wave mixing process in isotropic gyrotropic medium with spatial dispersion of cubic nonlinearity. Conservation of the total z-projections of both spin and orbital angular momenta of interacting waves is demonstrated. A simple classical and quantum interpretation of validity of the AM conservation law is given.