LACTIC OXIDASE OF PNEUMOCOCCUS

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Abstract
A lactic oxidase which specifically oxidizes L(+)-lactic acid can readily by isolated from a normal strain of Diplococcus pneumoneae, but not from a "Large colony" or LC strain. Procedures for fractionating the lactic oxidase are described. The enzyme is a flavoprotein. It can be resolved readily by acid ammonium sulfate into an inactive apoenzyme and an activator. Flavin mononucleotide can be used to activate the apoenzyme, but flavin adenine dinucleotide cannot. The pneumococcal lactic oxidase catalyzes the oxidation of lactate to acetate and CO2, with the expected stoichiometry. If catalase is added, O2 consumption is reduced by 50%, and pyruvate is the oxidation product. The inability of the LC strain to oxidize lactate is due to the absence of the enzyme and not to the presence of an inhibitor. The prosthetic group of the enzyme, presumably riboflavin mononucleotide. is present in the LC strain. The behavior of cell suspensions toward lactate and toward glucose was examined both for the normal and for the LC strain. The significance of the difference in behavior of the 2 strains is discussed. More information is required before the LC strain can be regarded as completely characterized with regard to enzyme differences from the normal. Special interest attaches to this problem because of the LC strain is subject to a transforming factor, as described by Ephrussi-Taylor.