Role of citritase in acetoin formation by Streptococcus diacetilactis and Leuconostoc citrovorum

Harvey, R. J. (University of California, Davis) and E. B. Collins. Role of citritase in acetoin formation by Streptococcus diacetilactis and Leuconostoc citrovorum. J. Bacteriol. 82:954-959. 1961.-Cell-free extracts of Streptococcus diacetilactis and Leuconostoc citrovorum converted citrate to acetate, oxalacetate, pyruvate, carbon dioxide, and acetoin. The products, stoichiometry, and cofactor requirements of the citrate-splitting reaction were identical to those reported for citritase. Coenzyme A was not required; the reaction was stimulated by magnesium or manganous ions, and inhibited by calcium ions. In S. diacetilactis the enzyme is constitutive; it has been found inducible in all other organisms that have been studied. Ten strains of S. diacetilactis, three strains of Leuconostoc, and one strain of S. liquefaciens contained the enzyme; 21 strains of S. cremoris and 3 strains of S. lactis did not. Cell-free extracts of S. diacetilactis and L. citrovorum converted pyruvate to acetoin and carbon dioxide in the presence of manganous ions and thiamine pyrophosphate.