Neuraminidase production by a Pasteurella haemolytica A1 strain associated with bovine pneumonia

Abstract

The properties of an extracellular neuraminidase produced by a Pasteurella haemolytica A1 strain (isolated from a case of bovine pneumonia) during growth in a defined medium were examined in this investigation. This enzyme, isolated from concentrated culture supernatants of P. haemolytica A1, was active against N-acetylneuramin lactose, human alpha 1-acid glycoprotein, fetuin, and bovine submaxillary mucin. Neuraminidase production paralleled bacterial growth in a defined medium and was maximal in the stationary phase of growth. The enzyme was purified to homogeneity by a combination of salt fractionation, ion-exchange chromatography on DEAE-Sephacel, and gel filtration on Sephadex G-200. These procedures yielded an enzyme preparation that possessed a specific activity of 100.62 μmol of sialic acid released per min per mg of protein against human alpha 1-acid glycoprotein. The K(m) value for this enzyme with human alpha 1-acid glycoprotein as the substrate was 1.1 mg/ml, and the enzyme possessed a pH optimum of 6.5. The P. haemolytica A1 neuraminidase had a molecular weight of approximately 150,000 as estimated by gel filtration and approximately 170,000 when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme was stable at 4°C for 3 h. At 37°C for 3 h, 25% of enzymatic activity was lost. Approximately 55% of the enzyme activity was lost within 30 min at 50°C, with greater than 70% of the enzyme activity being destroyed within 10 min at temperatures of ≥65°C.