Yasuko Kato

Improvement of Physicochemical and Enzymatic Properties of Bovine Trypsin by Non-enzymatic Glycation.

Bovine trypsin was modified with glucose through the Maillard reaction at 50°C and 65% RH for various periods (1 to 8 days). Tryptic activity against both benzoyl-L-arginine-p-nitroanilide and two protein substrates was enhanced with increases in the reaction period, and reached the maximum after a 4-day reaction. Although there were no big differences in pH dependency of trypsin activity between native and modified trypsins, the Km of the modified trypsin decreased to about half the native one. The modified trypsin retained its original activity almost completely after incubation in a buffer solution of pH 8.0 at 37°C for 72 h, while native trypsin was greatly inactivated. Furthermore, tryptic acitivity at high temperature, residueal activity after heating, and differential scanning calorimetric analysis showed that the modified trypsin was more heat-stable than native trypsin.

Analysis of Lactose-Protein Maillard Complexes in Commercial Milk Products by Using Specific Monoclonal Antibodies

Summary Lactose-protein Maillard complexes were immunochemically analyzed in various commercial milk products by ELISA and Immunoblotting using a specific monoclonal antibody. The Maillard complexes were detected in all samples analyzed, i.e., modified milk powder, skim milk powder, market pasteurized milk, milk beverages and concentrated milk. The apparent contents of Maillard complexes did not necessarily correlate to the loss of free amino groups, and the contents were generally higher in powdered milk products and milk beverages than in the market pasteurized milk. There appeared to be some relationship between the content of Maillard complexes and the time and temperature for pasteurization. Caseins were the major proteins detected by the antibody as lactose-protein Maillard complexes in various commercial milk products, though several whey proteins and unidentified polymerized proteins were also detected in some of the milk products. Thus, the monoclonal antibody was useful for in situ detection of lactose-protein Maillard adducts in milk and milk products.

Conformational stability of ovalbumin reacted with glucose in a maillard reaction.

Fig. 1. Disc Polyacrylamide Gel Electrophoretograms of OV and mOVG. Electrophoresis was carried out in 7.5% (w/v) polyacrylamide gels with a discontinuous buffer system.13) Protein samples (40/zg) were added to stacking gel at pH 7.0. The separation gel was run at pH 8.0. The buffer system was diethyl-barbituric acid-Tris (pH 7.0, 7= 0.02). The stabilization of protein has been widely investigated thermodynamically and/or kinetically in the presence of sugars,1>2) and it has been demonstrated that they stabilize protein against heat denaturation as determined by the scanning calorimetric method.1>3) On the other hand,