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Updated: Jun 27, 2026

Expression, Purification, Crystallization, and Enzyme Assays of Fumarylacetoacetate Hydrolase Domain-Containing Proteins
Published on: June 20, 2019
Aldo-keto reductases in which the conserved catalytic histidine is substituted
Luigi Di Costanzo1, Trevor M Penning, David W Christianson
1Department of Chemistry, Roy and Diana Vagelos Laboratories, University of Pennsylvania, Philadelphia, PA 19104-6323, United States. luigidi@sas.upenn.edu
Abstract:
Aldo-keto reductases (AKRs) are a major superfamily of monomeric NADPH-dependent carbonyl oxidoreductases. They are characterized by an (alpha/beta)(8)-barrel structure, which at its base contains a conserved catalytic tetrad of Tyr, Lys, His and Asp. Two AKR subfamilies contain other residues substituted for the catalytic His and perform different functions. First, the steroid 5beta-reductase (AKR1D1), which reduces CC double bonds instead of carbonyl groups, has a Glu substituted for His. Second, the Kvbeta subunits (AKR6A3, AKR6A5 and AKR6A9) which modulate opening of the voltage-gated potassium channel (Kv1) by oxidizing NADPH, have an Asn substituted for the His. Previously, we noted that conserved catalytic residues in AKRs perform similar functions in the short-chain dehydrogenases (SDRs). With the availability of crystal structures of AKR1D1 and two SDRs that catalyze double-bond reduction reactions, Digitalis steroid 5beta-reductase and 2,4-dienoyl-CoA reductase, we have compared their active sites to outline the features that govern whether 1,2-, 1,4- or 1,6-hydride transfer occurs.
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