Submitted to: Federation of European Microbiological Societies Microbiology Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/9/1999
Publication Date: N/A
Interpretive Summary: Pasteurella haemolytica is the causative agent of acute bovine pneumonic pasteurellosis or "shipping fever". This bacterial pathogen secretes an enzyme, neuraminidase, that has the capability of altering host cell surface properties and is considered a virulence factor for this organism. This study examined the effect of metal ions on the activity of the enzyme. .The results showed that manganese ion activates the enzyme. Therefore, inclusion of manganese in the enzyme assay will allow better detection of this enzyme virulence factor in culture supernatants and in whole-colony assays of isolates from pneumonic pasteurellosis.
Technical Abstract: Neuraminidase is one of the secreted hydrolytic enzymes present in a 24-hour culture supernatant of Pasteurella hemolytica, the causative agent of acute bovine pneumonic pasteurellosis. We determined the effect of 12 metal ions at 1, 5, and 10 mM concentrations on purified neuraminidase using bovine fetuin as substrate. Activity was determined by measuring the release of N-acetyl-neuraminic acid by using the thiobarbituric acid method. Of the 12 metal ions tested, manganese was the most effective in activating P. haemolytica neuraminidase. Activation by manganese was expressed as increased Vmax. The Km for fetuin remained unchanged at 98 æM. Equilibrium dialysis established that neuraminidase bound 2.14 mols of manganese per mol of enzyme with a Kd of 2.44 x 10-4 M. Although the kinetic plots appeared to indicate positive cooperativity with respect to manganese, a Hill coefficient of 0.989 was determined for the enzyme reaction. Inclusion of manganese in the assay for neuraminidase would improve detection of this important hydrolytic enzyme of P. haemolytica.