The aldo-keto reductase (AKR) superfamily: an update

The aldo-keto reductases (AKRs) are one of three enzyme superfamilies encom passing a range of oxidoreductases. Members of the AKR superfamily are mono meric (alpha/beta)(8)-barrel proteins, about 320 amino acids in length, whi ch bind NAD(P)(H) to metabolize an array of substrates. AKRs have been iden tified in vertebrates, invertebrates, plants, protozoa, fungi, eubacteria, and archaebacteria, implying that this is an ancient superfamily of enzymes . Earlier, in an attempt to clarify the confusion caused by multiple names for particular AKRs, we proposed a systematic and expandable nomenclature s ystem to assign consistent designations to unique members of the AKR superf amily. Since then, the number of characterized AKRs has expanded to 105 pro teins in 12 families. In addition, molecular cloning and genome sequencing projects have identified 125 potential AKR genes, many of which have no ass igned function. The nomenclature system for the AKR superfamily is accepted by the Human Genome Project. Using the earlier described nomenclature syst em, we now provide an updated listing of AKRs and potential superfamily mem bers. Information is also available at http://www.med.upenn.edu/akr. (C) 20 01 Elsevier Science Ireland Ltd. All rights reserved.