lactose + UDP + H(+) => D-glucose + UDP-alpha-D-galactose
lactose + udp + h(+) => d-glucose + udp-alpha-d-galactose
lactose + UDP + H(+) => D-glucose + UDP-alpha-D-galactose
lactose + udp + h(+) => d-glucose + udp-alpha-d-galactose