(S)-allantoin(in) + H(+)(in) => (S)-allantoin(out) + H(+)(out)
(s)-allantoin(in) + h(+)(in) => (s)-allantoin(out) + h(+)(out)
(S)-allantoin(in) + H(+)(in) => (S)-allantoin(out) + H(+)(out)
(s)-allantoin(in) + h(+)(in) => (s)-allantoin(out) + h(+)(out)