CROSS-LINKED STABILIZATION OF TRYPSIN WITH DEXTRAN-DIALDEHYDE

Dextran-dialdehyde was attached to trypsin molecules by incubation at 30 degrees C and pH 8.5. The cross-linking reaction was completed within a few hours, and the dextran-modified trypsin was isolated by gel filtration chromatography. The modified trypsin was resistant to auto-hydrolysis and a significant increases in thermal and pH stabilities was observed. Storage of modified trypsin at 4 degrees C under the optimum pH caused little loss of activity. The modified trypsin was resistant to organic solvents such as 10% ethanol and 0.2% sodium dodecylsulfate. Moreover, inhibition by soybean trypsin inhibitor was eliminated for the modified trypsin. Kinetic analysis indicated that access of a high-molecular-weight substrate (casein) to the modified enzyme was restricted compared with a low-molecular-weight substrate.