Arginase Immobilization on Poly(hydroxyethyl acrylate) Matrix Beads

Abstract

A study was made on the preparation and behaviour of polymer matrix im mobilized arginase, an enzyme involved in the urea cycle. Immobilization of purified calf liver arginase was obtained by a physical entrapment method based on the low temperature polymerization induced by radiation of a glass forming monomer mixed with an aqueous solution of the enzyme. Enzymatic activity was found to be retained in an acceptable range (30-35%) in a bead shaped matrix only when the monomer was hydroxyethylacrylate (HEA) purified by alkaline extraction and a particular sample preparation procedure was followed. The poly(hydroxyethyl acrylate) (PHEA) immobilized arginase was characterized by evaluating its chemical and enzymological properties such as K_m, activation energy, stability to proteolytic enzymes, and activity de pendence on pH. Performance runs of continuous biocatalytic conversion of ar ginine to ornithine were carried out utilizing a reactor consisting of a column with immobilized arginase beads. After weeks of operation the substrate con version remained almost constant, indicating a practically unaltered enzy matic activity. PHEA immobilized arginase beads also retained their activity for days either in the presence of whole blood or when implanted intraperi toneally or subcutaneously into rats. No significant inflammation or other adverse reactions were observed after one week of residence of such implants. This seems promising for lowering the arginine blood level in specific diseases.