The filamentous fungus Penicillium griseoroseum is an excellent pectinases producer. These enzymes are mainly used in textile and food industries. Our group has been studying the genetic and physiological aspects involved in the production of polygalacturonases (PG) in this fungus, which are pectinases with a great potential for industrial application.  We reported the isolation of two PG genes, pgg1 and pgg2, that encode the PGG1 and PGG2 enzymes, with predicted molecular masses of 38.4 and 38.3 kDa, and isoelectric point of 5.3 and 8.3 respectively. The PGG2 protein consists of 369 amino acids and has two putative glycosylation sites. The pgg2 gene is regulated by carbon source at the transcriptional level being repressed by glucose and expressed after 24 hours in pectin or sucrose and yeast extract. In order to evaluate the contribution of PGG2 in the total PG activity, a disruption vector, named pPG15pgg2Dniafo, was constructed by inserting a 4 Kb HindIII DNA fragment containing the niaD gene from Fusarium oxysporum in the coding region of pgg2. The P. griseoroseum niaD^– PG63 mutant, which is unable to grow on nitrate as sole nitrogen source, was used as host strain for transformation. We obtained 650 transformants, among which two were showed to contain an inactivated pgg2 copy by Southern Blot analysis. The disruption of pgg2 resulted in transformant strains producing at most 12% of PG activity of the PG63 mutant indicating that this gene responds for almost 90% of PG total activity in P. griseoroseum.