Stability and properties of mushroom tyrosinase entrapped in alginate, polyacrylamide and gelatin gels

Properties of tyrosinase (EC 1.14.18.1) from mushroom, immobilized by entrapment in polyacrylamide, alginate and gelatin gels were examined. Maximum activity immobilization yield of 88% was obtained in gelatin followed by 67 and 57% in Cu-alginate and polyacrylamide gels, respectively. The enzyme entrapped in alginate and polyacrylamide gels exhibited broader pH activity profile while in the case of gelatin a shift of pH optimum toward alkaline side, as compared to the soluble enzyme, was observed. The temperature optima for the soluble enzyme was 20°C and it shifted to 35 and 40°C after entrapment of the enzyme in alginate and gelatin gels, respectively. The enzyme embodied in gelatin showed greater storage stability as well as thermal stability at 40°C compared to the other preparations. It was demonstrated that the immobilized enzyme could be used repeatedly, after intermittent storage, for production of L-DOPA (3,4-dihydroxyphenylalanine). Cu-alginate entrapped tryosinase was found to be superior in this regard. The enzyme in gelatin gels retained about 30% of its initial activity after 8 cycles of use. The results indicate a possibility of employing gel entrapped tyrosinase from mushrooms for construction of bioreactors for production of L-DOPA.