Physico-chemical characterization of the main factors affecting the mode of action of liver alcohol dehydrogenase immobilized on nylon tubing

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Abstract
Alcohol dehydrogenase (ADH) from horse liver (EC 1.1.1.1), cross‐linked through the bifunctional reactive glutaraldehyde, onto nylon tubing was immobilized (35 μg cm−2 internal surface of nylon tubing). ADH inactivation kinetics of the immobilized enzyme are of first order (t1/2 = 84.3 h, k = 5.2 × 10−3 h−1 at 5°C; t1/2 = 2.6h, k = 0.26 h−1 at 50°C). The activity versus pH profile points to a smaller effect of pH on the activity of the enzyme, which is the case of ADH in solution, explicable on the basis of limitations to proton diffusion towards/from the support. A limiting effect to free external diffusion of the substrate (products) towards/from the support was observed; this effect seems to determine the effective kinetic behaviour of immobilized ADH.