The important Phase I enzymes present in the kidney are cytochrome P450, prostaglandin synthase, and prostaglandin reductase. The Phase I enzyme cytochrome P450 is present in the kidney at 10% of the level of the liver. Important Phase II enzymes present in the kidneys are UDP-glucuronosyltransferases(UGT, sulfotransferases, and glutathione-S-transferase