 UGT2B7 is the major enzyme isoform for the metabolism of morphine to the main metabolites, morphine-3-glucuronide (M3G) which has no analgesic effect and morphine-6-glucuronide (M6G), which has analgesic effects more potent than morphine.As a consequence, altered UGT2B7 activity can significantly affect both the effectiveness and side-effects of morphine, as well as some related opiate drugs.No structure of a full human UGT enzyme has been determined yet, however Miley et al.