Comparative study of intracellular and extracellular pectinases produced by Penicillium frequentans

The filamentous fungus Penicillium frequentans synthesized eleven polygalacturonases (PGs) and two pectinesterases (PEs) when grown in liquid culture supplemented with pectin. Seven PGs and the two PEs were secreted in the medium, whereas four PGs were not secreted. Among the secreted PGs, the endo-PG (band 10) and exo-PGs (band 5) were the enzymes secreted at the highest levels. All secreted PGs bound to lectin and their secretion and/or enzymic activities were inhibited by tunicamycin (TM), except for the constitutive and inducible endo-PG (band 10). Studies on the affinity for concanavalin A (ConA) and the effect of TM suggested that the secreted endo-PG and exo-PG differed in level and process of glycosylation. The exo-PG was characterized as a N-glycoprotein, whereas the endo-PG is probably an O-glycoprotein. The PGs (bands 3 and 4) were neither bound to ConA nor secreted and their enzymic activities were inhibited by TM, suggesting that they are probably N-glycoproteins with complex oligosaccharides of type three and tetra-antennary structure. The other PGs (bands 6 and 8) that were not secreted and did not bind to ConA were not inhibited by TM. These enzymes presented chromatographic characteristics and effects with TM that were similar to endo-PG (band 10), because these PGs might be unglycosylated or/and aggregate forms of the endo-PG (band 10).