COVALENT IMMOBILIZATION OF A HYDROPEROXIDE LYASE FROM MUNG BEANS (PHASEOLUS-RADIATUS L.)

A fatty acid hydroperoxide lyase of mung beans has been covalently imm obilized on different commercially available gels which represents the first immobilization of this type of enzyme from a higher plant. Ultr aLink lodoacetyl possessed optimum coupling properties and yielded a m aximum activity of 1.3 U ml(-1) gel and a yield of 84%. The effect of various protective reagents (e.g. thiols, antioxidants) and of the sub strate concentration on the re-usability of the immobilized enzyme was investigated. Compared to a control, the relative activity during re- use was enhanced 1.8- to 2.3-fold in the presence of dithiothreitol. A s the hydroperoxide lyase was irreversibly inhibited by the substrate, its re-usability depended strongly on the hydroperoxide concentration . The lowest inactivation was with 55 mu M hydroperoxide which resulte d in a relative activity of 73% after the third cycle. The storage sta bility of the hydroperoxide lyase was significantly improved by immobi lization and resulted in a relative activity of 86% after 18 days, whe reas the soluble enzyme lost 68% of its initial activity.