PURIFICATION AND CHARACTERIZATION OF 2 ACETYL XYLAN ESTERASES FROM PENICILLIUM-PURPUROGENUM

Penicillium purpurogenum produces several enzymes active in xylan hydr olysis, of there, the acetyl xylan esterase (AXE) activity secreted by the fungus has now been studied. The amount of activity obtained in t he culture is related to the degree of acetylation of the carbon sourc e used, the best being chemically acetylated xylan. AXE was concentrat ed from culture supernatants by ultrafiltration and (NH4)(2)SO4 precip itation and fractionated by gel filtration in Bio-Gel P-300. Two peaks of activity (AXE I and AXE II) were obtained. These two enzymes were further purified separately to homogeneity by chromatography in CM-Sep hadex C-50 and chromatofocusing. AXE I (M(r) 48 000) has a pI of 7.5, while AXE II (M(r) 23 000) has a pI of 7.8. Optimal enzyme activity wa s at pH 5.3 and 50 degrees C for AXE I and pH 6.0 and 60 degrees C for AXE II. Both enzymes are active towards several acetylated substrates . Antisera against the two enzymes do not cross-react, and the N-termi nal sequences of AXE I and II do not show similarities. These results suggest that AXE I and AXE II are the products of different genes.