Immobilization of single-strand specific nuclease (S1 nuclease) from Aspergillus oryzae

S1 nuclease from Aspergillus oryzae (EC 3.1.30.1) was coupled to gelatin-alginate composite matrix using the residual free aldehyde groups on the surface of glutaraldehyde crosslinked matrix. The immobilized enzyme retained approximately 10% activity of the soluble enzyme. When partially purified enzyme was bound to the matrix, the immobilized preparation did not show any detectable enzyme activity. However, the activity could be restored when the coupling was carried out in the presence of a coprotein or substrate. The optimum pH of the immobilized S1 nuclease shifted to 3.8 from 4.3 for the soluble enzyme. Also, optimum temperature increased to 65 degrees C after immobilization. Bound S1 nuclease showed increased pH and temperature stabilities. Immobilization brought about a twofold decrease in the Michaelis-Menton constant (Km).