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Open Access Research article

A genomic survey of proteases in Aspergilli

Sebnem Ozturkoglu Budak123, Miaomiao Zhou13, Carlo Brouwer1, Ad Wiebenga13, Isabelle Benoit13, Marcos Di Falco4, Adrian Tsang4 and Ronald P de Vries13*

Author Affiliations

1 CBS-KNAW Fungal Biodiversity Center, Uppsalalaan 8, Utrecht 3584 CT, The Netherlands

2 University of Ankara, Faculty of Agriculture, Department of Dairy Technology, Ankara, Turkey

3 Fungal Molecular Physiology, Utrecht University, Utrecht, The Netherlands

4 Centre for Structural and Functional Genomics, Concordia University, 7141 Sherbrooke Street West, Montreal, QC H4B 1R6, Canada

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BMC Genomics 2014, 15:523  doi:10.1186/1471-2164-15-523

Published: 25 June 2014

Abstract

Background

Proteases can hydrolyze peptides in aqueous environments. This property has made proteases the most important industrial enzymes by taking up about 60% of the total enzyme market. Microorganisms are the main sources for industrial protease production due to their high yield and a wide range of biochemical properties. Several Aspergilli have the ability to produce a variety of proteases, but no comprehensive comparative study has been carried out on protease productivity in this genus so far.

Results

We have performed a combined analysis of comparative genomics, proteomics and enzymology tests on seven Aspergillus species grown on wheat bran and sugar beet pulp. Putative proteases were identified by homology search and Pfam domains. These genes were then clusters based on orthology and extracellular proteases were identified by protein subcellular localization prediction. Proteomics was used to identify the secreted enzymes in the cultures, while protease essays with and without inhibitors were performed to determine the overall protease activity per protease class. All this data was then integrated to compare the protease productivities in Aspergilli.

Conclusions

Genomes of Aspergillus species contain a similar proportion of protease encoding genes. According to comparative genomics, proteomics and enzymatic experiments serine proteases make up the largest group in the protease spectrum across the species. In general wheat bran gives higher induction of proteases than sugar beet pulp. Interesting differences of protease activity, extracellular enzyme spectrum composition, protein occurrence and abundance were identified for species. By combining in silico and wet-lab experiments, we present the intriguing variety of protease productivity in Aspergilli.