Filamentous fungi are widely exploited for their capacity of high level secretion of enzymes. Molecular genetic approaches for strain improvement have shown that this ability can also be extended to many other proteins of fungal origin. However, a major exception to this rule seems to be high level secretion of fungal metallo-proteins. So far, attempts to overproduce this type of enzymes in recombinant fungal systems have had limited success. To gain insight into the bottle-necks existing for the (over)production of metallo-proteins in filamentous fungi, we have started a project to study the expression of genes encoding heme-containing fungal peroxidases in Aspergillus niger. Three genes were chosen for this study: lignin peroxidase (IipA) and manganese peroxidase (mnpl) encoding genes from Phanerochaete chrysosporium and the chloroperoxidase (cpo) encoding gene from Caldariomyces fumago. Different expression cassettes for each of the three genes have been constructed and used to transform a protease deficient strain of Aspergillus niger. Analysis of the transformants shows expression for all three genes. Manganese peroxidase and chloroperoxidase are both produced as active extracellular enzymes while lignin peroxidase is incorrectly processed resulting in an inactive extracellular protein. Further analysis of the limiting factors for peroxidase overproduction is in progress and will be presented.
Fungal Genet. Newsl. 46 (Supl):
Full conference title:
Fungal Genetics Conference 20th
- Fungal Genetics Conference 20th (1999)