(R)-glycerate(out) + H(+)(out) => (R)-glycerate(in) + H(+)(in)
(r)-glycerate(out) + h(+)(out) => (r)-glycerate(in) + h(+)(in)
(R)-glycerate(out) + H(+)(out) => (R)-glycerate(in) + H(+)(in)
(r)-glycerate(out) + h(+)(out) => (r)-glycerate(in) + h(+)(in)