[Human drug metabolizing enzymes. II. Conjugation enzymes]

In this review we focus on human conjugation enzymes (UDP-glucuronyltransferases, methyl-trasferases, N-acetyl-transferases, O-acetyl-transferases, Amidases/carboxyesterases, sulfotransferases, Glutation-S-transferases and the enzymes involved in the conjugation with amino acids) that participate in the metabolism of xenobiotics. Although conjugation reactions in most of the cases result in detoxication, more and more publications prove that the reactions catalysed by these enzymes very often lead to activated molecules that may attack macromolecules (proteins, RNAs, DNAs), resulting in toxicity (liver, neuro-, embryotoxicity, allergy, carcinogenecity). We have summarised the data available on these enzymes concerning their catalytic profile and specificity, inhibition, induction properties, their possible role in the generation of toxic compounds, their importance in clinical practice and drug development.