PURIFICATION AND CHARACTERIZATION OF AN EXTRACELLULAR ASPARTIC PROTEINASE FROM ASPERGILLUS-FUMIGATUS

An aspartic proteinase (PEP) from the culture supernatant of a clinica l isolate of Aspergillus fumigatus was purified to virtual homogeneity at a yield of 24%. The procedure involved affinity chromatography on pepstatin agarose, the interaction requiring a chaotropic salt (sodium trifluoroacetate) for complete elution of the enzyme. Among 11 amino acids of the N-terminal region, nine were identical with the correspon ding sequence of the aspartic proteinase aspergillopepsin A from Asper gillus niger var. awamori (previously called Aspergillus awamori). Thu s PEP belongs to the aspergillopepsins, a family of closely related as partic proteinases produced by aspergilli. Specific antibodies against PEP were detected by dot blot assay in sera of two patients with aspe rgillosis. In addition, PEP antigen was demonstrated by immunofluoresc ence in mycotic human lung, using specifically elicited antibodies fro m guinea-pigs. PEP had an estimated molecular mass of 38 kDa and the p i was determined at pH 4.2. PEP is therefore likely to be closely rela ted to an acid proteinase of A. fumigatus which was originally describ ed in 1981.