Purification and partial characterisation of a novel trypsin-like cysteine protease from Metarhizium anisopliae

Trypsin-like enzymes from the entomopathogenic fungus Metarhizium anisopliae have been characterised. Two proteases with tryptic activity were purified by narrow range isoelectric focussing and affinity chromatography. One of these proteases, with an isoelectric point of 5.4 and a molecular mass of 28.8 kDa is a ‘classical’ trypsin belonging to the serine protease class. The other protease, with an isoelectric point of 4.6 and a molecular mass of 26.7 kDa, demonstrates trypsin-like specificity but, on the basis of inhibition and activation studies, belongs to the cysteine protease family and as such is the first fungal protease to be found of this type. The amino acid composition, kinetic constants and activity against proteinaceous substrates, including locust cuticle have been determined.