The capability of Pasteurella multocida to secrete proteases to the culture
medium and their characterization were studied in five animal isolates (bo
vine, chicken, sheep, and two from pig). All the isolates produced protease
s in a wide range of molecular mass. It is suggested that they are neutral
metalloproteases, since they were optimally active between pH 6 and 7, inhi
bited by chelating agents but not by other protease inhibitors, and reactiv
ated by calcium. Proteases from isolates were able to degrade IgG. Several
proteins from supernatants of cultures precipitated with 70% (NH4)(2)SO4 of
all the P. multocida isolates were recognized by a polyclonal antiserum ra
ised against a purified protease from Actinobacillus pleuropneumoniae. Prot
ease production might play an important role during tissue colonization and
in P. multocida diseases.