Fetuin is a substrate for Pasteurella haemolytica O-sialoglycoprotease

A soluble bovine glycoprotein, fetuin, was used as an alternative substrate to identify O-sialoglycoprotease activity in culture supernatant protein fractions of Pasteurella haemolytica. An aliquot of a 24-hour incubation mixture containing fetuin and O-sialoglycoprotease was denatured and examined after gradient sodium dodecyl polyacrylamide gel electrophoresis. The Coomassie-Brilliant-Blue-stained gel was examined for the disappearance of the fetuin band at an apparent molecular mass of 64 KDa. Four major hydrolysis products were identified: an N-terminal fragment of 45 kDa, a 20 kDa fragment at Val50, and two C-terminal fragments at Val273 and His287.