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(+)