An Escherichia coli mutant deficient in pyruvate oxidase activity due to altered phospholipid activation of the enzyme.

The pyruvate oxidase (pyruvate:ferricytochrome b(1) oxidoreductase, EC 1.2.2.2) of Escherichia coli is markedly activated by phospholipids in vitro. To test the physiological relevance of this activation, we isolated an E. coli mutant producing an oxidase that is deficient in activation by (and binding to) phospholipids. The mutant oxidase could be fully activated by a specific proteolytic cleavage, indicating that the catalytic site is normal. The mutant enzyme functions poorly in vivo, indicating that activation of the oxidase by phospholipids plays an important physiological role.