Purification and Characterization of Endo- and Exo-polygalacturonases from Fomitopsis cytisina

Abstract

Three polygalacturonases (PGs) were purified homogeneously in SDS-PAGE from the culture filtrate of white rot basidiomycete, Fomitopsis cytisina . By analysis of reaction products, two of three PGs were concluded to be endo-type (endoPG I and II) and the other to be exo-type (exoPG) . Molecular masses of endoPG I and II were both estimated to be 38 kDa and that of exoPG 50-60 kDa. Their molecular masses by deglycosylating with EndoH decreased by 37, 37 and 44 kDa, respectively. Isoelectric points of endoPG I, II and exoPG were 4.3, 4.2 and 4.0, respectively . Their amino acid compositions were similar to one another and furthermore, endoPG I and II were very similar in the 20 amino acids sequence of N-terminal. Their properties, including their kinetic parameters, were determined. Both endoPG I and II could act more on oligo- and polyGalUAs than hepta of DP and endoPG II could act on tri- and diGalUA. The characteristics of endoPGs from this fungus showed considerable difference from that of Stereum purpureum in spite of allogeneic white rot basidiomycete, being classified under the same Aphyllophorales as S. purpureum. ExoPG had the highest activity on nonaGalUA and, like plants exoPG, could not act on 4, 5-unsatd. oligoGalUA.