Identification of the reactive cysteine residue in human placenta aldose reductase.
Modification of human placental aldose reductase by iodoacetate (IAA) led to a mol/mol binding of IAA, a 40% decrease in the kcat, a 3-5-fold increase in the Km,NADPH and Km,glyceraldehyde and a 600-fold increase in the Ki,sorbinil; determined at pH 6.0. NADPH and 2'-monophosphoadenosine 5'-diphosphoribose but neither glyceraldehyde nor sorbinil, prevented carboxymethylation-induced changes. Cleavage of [14C]IAA-modified enzyme by trypsin resulted in two radiolabeled peptides: Val-297 to Lys-307 and Val-297 to Phe-315. In both these peptides Cys-298 was the only radiolabeled residue. It is suggested that Cys-298 regulates the kinetic and inhibition properties of the enzyme, but does not participate in catalysis.
Liu
S Q
SQ
Department of Human Biological Chemistry and Genetics, University of Texas Medical Branch, Galveston 77555.
Bhatnagar
A
A
Ansari
N H
NH
Srivastava
S K
SK
D000246:Adenosine Diphosphate Ribose / Q000031:analogs & derivatives / Q000494:pharmacology; D000449:Aldehyde Reductase / Q000037:antagonists & inhibitors / Q000737:chemistry*; D000595:Amino Acid Sequence; D001665:Binding Sites; D002250:Carbon Radioisotopes; D003545:Cysteine / Q000032:analysis*; D006801:Humans; D007461:Iodoacetates; D019807:Iodoacetic Acid; D007700:Kinetics; D008969:Molecular Sequence Data; D009249:NADP / Q000494:pharmacology; D010920:Placenta / Q000201:enzymology*; D014357:Trypsin
D002250:Carbon Radioisotopes; D007461:Iodoacetates; C020857:phosphoadenosine diphosphoribose; D000246:Adenosine Diphosphate Ribose; D009249:NADP; D000449:Aldehyde Reductase; D014357:Trypsin; D003545:Cysteine; D019807:Iodoacetic Acid