Published online by Cambridge University Press: 05 June 2009
Proteolytic enzymes present in extracts of third (L3) and fourth (L4) stage larvae and adults of the cattle nematode Ostertagia ostertagi were defined on the basis of pH optima and proteinase inhibitor sensitivity in spectrophotometric assays using azocasein and elastin-orcein as protein substrates. Evidence that different classes of proteinases are expressed in a stage specific manner was provided by the contrasting pH optima and inhibitor sensitivities shown by the enzymes in the different parasite stages. Stage specificity was confirmed by gelatin-substrate analysis. In addition, proteolytic activity was sought in the excretory/secretory products (ES) of the L4 following simple in vitro culture. Contrasting pH and inhibitor sensitivities as well as gelatin-substrate analysis showed that different proteinases were present in somatic L4 extracts and L4 ES products. The secreted proteinases may be useful targets for serodiagnosis or vaccination.
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