The metabolism of protocatechuate by Pseudomonas testosteroni

1. Protocatechuate 4,5-oxygenase, purified 21-fold from extracts of Pseudomonas testosteroni, was examined in the ultracentrifuge and assigned a mol.wt. of about 140000. 2. When diluted, the enzyme rapidly lost activity during catalysis. Inactivation was partially prevented by l-cysteine. 3. With a saturating concentration of protocatechuate (1.36mm), K(m) for oxygen was 0.303mm. This value is greater than the concentration of oxygen in water saturated with air at 20 degrees . 4. Cell extracts converted protocatechuate into gamma-carboxy-gamma-hydroxy-alpha-oxovalerate, which was isolated as its lactone. 5. gamma-Carboxy-gamma-hydroxy-alpha-oxovalerate pyruvate-lyase activity was stimulated by Mg(2+) ions and mercaptoethanol. Cells grown with p-hydroxybenzoate as carbon source contained higher concentrations of this enzyme than those grown with succinate.