Mode of action of endopolygalacturonase immobilized by adsorption and by covalent binding via amino groups

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Abstract
Action pattern of endopolygalacturonase (E.C.3.2.1.15) immobilized by adsorption on porous powdered poly(ethyleneterephthalate) and covalently bound via amino groups on poly(2, 6‐dimethyl‐p‐phenyleneoxide) and poly(6‐caprolactame), respectively, were investigated in suspension and packed columns using polymeric and oligomeric D‐galactosiduronates as substrates. The covalent binding invariably led to a lowering of randomness of degradation of high‐molecular substrates and loss of specificity of (3 + 1) splitting of tetra(galactosiduronic acid), typical of the free enzyme. In the adsorbed endopolygalacturonase the degree of randomness of degradation of D‐galacturonan and Km,app value were dependent on the substrate transfer; the former parameter increased, the later decreased with increasing flow‐rate of the substrate through the immobilized enzyme bed. The action pattern on low‐molecular substrates was not altered. The changes in action pattern of the covalently immobilized endopolygalacturonase are ascribed to sterical limitations resulting from a binding of the enzyme molecule in the proximity of its active site. In endopolygalacturonase bound to the support by hydrophobic interactions external diffusion effects are regarded the factors governing the enzyme action.