PURIFICATION AND CHARACTERIZATION OF NADPH-DEPENDENT 2-OXOALDEHYDE REDUCTASE FROM PORCINE LIVER - A SELF-DEFENSE ENZYME PREVENTING THE ADVANCED STAGE OF THE MAILLARD REACTION

An enzyme which catalyzes the reduction of 3-deoxyglucosone to 3-deoxyfructose and methylglyoxal to acetol, was isolated and purified from porcine liver. 2-Oxoaldehyde compounds were found to be especially good substrates and monocarbonyl compounds were poor substrates for this reductase. The optimum pH of the enzyme activity was 6.5. The K(m) for 3-deoxyglucosone and methyglyoxal were 2.1 mM and 3.3 mM, respectively. The enzyme consisted of a single polypeptide chain with a molecular mass of 38 kDa. The activity of the enzyme was completely inhibited by p-chloromercuribenzoate. The enzyme inhibited the advanced stage of the Maillard reaction.