Characterization of the cardiolipin synthetase activity of Escherichia coli envelopes

The synthesis of cardiolipin from phosphatidylglycerol catalyzed by isolated envelopes of Escherichia coli occurs without the utilization of endogenous CDP-diglyceride as a substrate. The synthesis of cardiolipin has been assayed distinct from the synthesis of bis-phosphatidic acid. Envelope fractions isolated from cultures exposed to treatments which increase the relative rate of cardiolipin synthesis in vivo were found not to have increased amounts of cardiolipin synthetase activity in vitro. We suggest that the relative increase of cardiolipin synthesis observed during these treatments stems from the lack of an energy requirement for the cardiolipin synthetase reaction and the presence of large amounts of cellular phosphatidylglycerol.