Flow kinetics of L-asparaginase attached to nylon tubing.

Abstract

AbstractL‐Asparaginase has been attached by chemical means to the inner surface of nylon tubing. An experimental study has been carried out of the flow kinetics for such a system, asparagine solutions at various concentrations being passed through two lengths of tubing at various flow rates. Measurements were made of the concentration of the product ammonia at the tube exit, and of the rate of formation of ammonia, under the various conditions. Apparent Michaelis constants, Km(app), were some three orders of magnitude higher than the Km for the enzyme in free solution (∼13 × 10−6JM). The results were analyzed with respect to the theoretical treatment described in the preceding paper (Kobayashi and Laidler), three different methods being employed. It is concluded that at lower substrate concentrations and flow rates the reactions are largely diffusion‐controlled, the enhanced Km(app) values being largely if not entirely due to the diffusion control; ionic strength studies showed electrostatic repulsion effects to be unimportant. At high concentrations and high flow rates (when the diffusion layer is of negligible thickness) the diffusional effects are minimized, and Km(app) approaches the true Km value for the immobilized enzyme.