Comparison of reactivity of alkene epoxidation with intact cells and cell-free extracts of Methylosinus trichosporium OB3b

Kinetic studies of a series of alkene epoxidations (ethylene, propylene and 1-butene) with intact cells and cell-free extracts of Methylosinus trichosporium OB3b were carried out. For the epoxidation with intact cells, V_max values were independent of the type of alkenes. K_m values, however, were remarkably different, and the order was ethylene < propylene < 1-butene. The results suggest that the reactivity of alkene epoxidation with intact cells of M. trichosporium OB3b strongly depends on the affinity of alkene and methane monooxygenase. For cell-free extracts, V_max values for ethylene and propylene were almost the same. V_max value for 1-butene was extremely small. K_max values were remarkably different, and the order was ethylene < propylene < 1-butene. On the comparison of intact cells and cell-free extracts of M. trichosporium OB3b, the K_max value of ethylene with intact cells was much smaller than that with cell-free extracts, indicating that ethylene is more easily incorporated into the cells. On the other hand, propylene and 1-butene are not easily incorporated on comparison of the K_max values of intact cells with those of the cell-free extracts. These results indicate that the cell membrane may act to avoid higher alkenes.