Photochemical immobilization of cucurbita fruit ascorbate oxidase onto polyethylene disc for determination of ascorbate in serum and foodstuffs

Abstract

An ascorbate oxidase purified from the green fruit of zucchini squash (Cucurbita pepo medullosa) was immobilized photochemically on a polyethylene disc with 85% retention of initial activity of free enzyme. The optimum pH (5.5) was unchanged, while K m was decreased. The polyethylene discs were employed for determination of ascorbic acid in serum and foodstuffs. The working linear range was 2.8 μM to 16 μM. The mean value of ascorbic acid in serum as measured by the method was 0.16 mg/dl in males and 0.209 mg/dl in females. The immobilized enzyme was used 100 times over 4 months, when stored at 4°C. © 2011 Informa Healthcare USA, Inc.