PURIFICATION AND CHARACTERIZATION OF 4 POLYGALACTURONASES FROM BOTRYTIS-CINEREA

An isolate of Botrytis cinerea produced four polygalacturonases (PGs) in a modified Czapek-Dox liquid medium containing citrus pectin. Purification involving liquid-phase isoelectric focusing, ion-exchange chromatography and concanavalin A-affinity chromatography revealed two endo-PG isozymes (endo-PGI and endo-PGII) with pl values of 8.8 and 4.9 and two exo-PGs (exo-PGI and exo-PGII) with pI values of 4.9 and 3.5 in 10-day-old cultures. Endo-PGI and II both had apparent M(r) values of 36 kDa; exo-PGI and II had M(r) values of 65 and 70 kDa respectively. Each protein consisted of a single polypeptide chain. Exo-PGI and II were shown to be glycoproteins by their affinity to concanavalin A. The temperature optima for endo-PGI, endo-PGII exo-PGI and exo-PGII were 37, 34, 48 and 50-degrees-C respectively, and all the isozymes showed optimal pH values between 4.0 and 5.0.