Inorganic pyrophosphatase of Streptococcus faecium F24

Abstract

The acid Co2+-activated and the alkaline Mg2+-activated inorganic pyrophosphatases of Streptococcus faecium F24 were studied by a variety of techniques to determine whether they are activities of two distinct proteins or of a single protein. Both enzyme activities were found to be cryptic and soluble. The specific activities of both enzymes increased coordinately 1.5- to 3-fold during exponential growth at 37C, and then decreased as the cells approached stationary phase. Similar shifts in specific activity did not occur upon growth at 30C. The specific activities in extracts of cells in stationary phase varied coordinately over a 2-fold range depending on nutritional conditions. Diethylaminoethyl cellulose (DEAE-cellulose) and Sephadex G-100 column chromatography and starch–gel electrophoresis did not resolve the two activities. Slight differences in the thermal inactivation kinetics of the two activities were observed. It was concluded that the two pyrophosphatase activities are most probably those of a single protein under different assay conditions.