Function with symbolic terms

I need that this function gives me back another function dependent on alph:

function [f_alpha] = valor_funcao2(func,d,x)

syms f(x1,x2)

f(x1,x2) = str2sym(func);

alph = zeros(1,2,'sym');

x(end,:) = x(end-1,:) - grad.*alph;

syms f_alpha

f_alpha = func(alph(1),alph(2));