Coenzyme production using immobilized enzymes. I. Preparation, characterization, and laboratory-scale application of an immobilized NAD super(+) kinase

NAD super(+) kinase (ATP:NAD super(+) 2-phosphotransferase, EC 2.7.1.23) isolated from chicken liver was immobilized on a silica-based support possessing aldehyde functional groups. The highest catalytic activity achieved was 16 U g super(-1) solid. The optimal pH for the catalytic activity of the immobilized NAD super(+) kinase was pH 7.1-7.3. The apparent optimum temperature for the immobilized enzyme was about 5 degree C higher than that of the soluble enzyme. There were no significant differences in the K sub(mapp) values. The immobilization improved the conformational stability of the enzyme. In preliminary experiments, a 95% conversion of NAD super(+) to NADP super(+) was achieved with use of the immobilized NAD super(+) kinase, which preserved its starting activity practically unchanged up to 36 days.