Identification and characterization of a second polygalacturonase gene of Aspergillus niger

The filamentous fungus Aspergillus niger produces several endopolygalacturonases that are involved in the degradation of pectin. PGI, the enzyme representing the second most abundant activity in a commercial enzyme preparation, was further characterized and the corresponding gene was isolated. The nucleotide sequence of the pgaI gene was determined and the protein coding region was found to be interrupted by two short introns, one of which has a unusual donor splice site. The deduced 368 amino acids long protein with a putative prepropeptide of 31 amino acids shows 60% sequence identity to PGII in the mature protein. PGI overproducing A. niger strains were obtained by cotransformation with the cloned gene.