L-phenylalanine(out) + L-serine(in) => L-phenylalanine(in) + L-serine(out)
l-phenylalanine(out) + l-serine(in) => l-phenylalanine(in) + l-serine(out)
L-phenylalanine(out) + L-serine(in) => L-phenylalanine(in) + L-serine(out)
l-phenylalanine(out) + l-serine(in) => l-phenylalanine(in) + l-serine(out)