THE OXIDATION OF SUCCINATE IN EXTRACTS OF XANTHOMONAS PHASEOLI
Succinoxidase and succinic dehydrogenase were found in cell-free extracts of Xanthomonas phaseoli, obtained by sonic oscillation, and remained largely in the supernatant solution after ultracentrifugation. The effect of time of exposure of the cells to sonic oscillation on cell breakage was found to follow first order reaction kinetics, as was the "solubilization" of succinic dehydrogenase and succinoxidase. It appears that the two enzymatic activities are released from the cell in a particulate form which is further fragmented on continued treatment in the sonic oscillator.The clear supernatant solution obtained after ultracentrifugation of the cell-free extract was found to contain those members of the electron transport chain which had previously been found in the intact cell, namely, flavoprotein and cytochromes b1, a1, and a2. These substances could be reduced by the addition of succinate. Malonate prevented this reduction. The effects of various inhibitors on the succinoxidase system and on succinic dehydrogenase are presented and discussed in relation to the operation of the electron transport chain in the oxidation of succinate by this organism.