Isolation and characterization of aldose reductase from calf brain.
Aldose reductase activity (alditol: NADP+ 1-oxidoreductase, EC 1.1.1.21) from calf brain was separated into two protein fractions by DEAE chromatography. Further purifcation by molecular sieve chromotography and electrofocusing yielding two distinctive enzymes, which were designated AR I and AR II. AR I was purified 646-fold and found to have an isoelectric point of 6.18. AR I was most active as a monomer with a molecular weight of 29 000 and appeared to be in equilibrium with a less active dimer. AR II was purified 425-fold and found to have an isoelectric point of 4.88. The molecular weight of this enzyme was 30 000. Although both enzymes had specificity for aldoses as substrates, AR I had two to three times larger turnover numbers with aromatic aldehydes and hexonates than did AR II. AR I was activated by sulfhydryl compounds and exhibited biphasic double reciprocal plots. AR I was more sensitive to inhibition by high substrate and phenobarbital concentrations than was AR II. AR I and AR II did not have antigenic similarity as tested by Ouchterlony immunodiffusion and counter immunoelectrophoresis. An immunochemical cross-reaction was observed  between AR II and lens aldose reductase.
D000429:Alcohol Oxidoreductases / Q000378:metabolism*; D000449:Aldehyde Reductase / Q000302:isolation & purification / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000201:enzymology*; D002417:Cattle; D003378:Counterimmunoelectrophoresis; D003429:Cross Reactions; D006863:Hydrogen-Ion Concentration; D005779:Immunodiffusion; D007527:Isoenzymes / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D046911:Macromolecular Substances; D008970:Molecular Weight; D013329:Structure-Activity Relationship
D007527:Isoenzymes; D046911:Macromolecular Substances; D000429:Alcohol Oxidoreductases; D000449:Aldehyde Reductase