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 <=> lactose + udp + h(+)