Preliminary Study Of Polysaccharide Deacetylase COD4 Function From Aspergillus Fumigatus

Aspergillus fumigatus is the most common clinical saprophytic fungus,which can cause a high risk pathogen infection.Cell wall structure of Aspergillus fumigatus is uniquent compared with human cell and important for self-protection,so it has been the ideal drug target for anti-fungal infection drugs prduction.In-depth understanding of cell wall polysaccharide metabolic process is important.The polysaccharide deacetylase is a important hydrolase in metabolic processes of polysaccharide which belongs to the carbohydrate esterase family 4(CE4),including chitin deacetylase,acetyl xylan esterase,xylanase,Rhizobium NodB chitin oligosaccharides deacetylase and peptidoglycan deacetylase.Using bioinformatics method,we found seven genes,namly cod1-cod7,in Aspergillus fumigatus,which have high homology with NodB.In this thesis,we focused on functional analysis of the cod4 gene.We cloned and expressed the gene in E.coli.The molecular weight of recombinant COD4 protein is 35.2kDa.After purification by affinity chromatography,ion-exchange chromatography and gel filtration,COD4 was purified and ready for crystallization.Biochemical analysis showed that COD4 was able to hydrolyze acetyl group from chitobiose,chitotriose,but COD4 was inactive to chitooligosaccharide with polymerization degree higher than 5.Based on our biochemical and genetical analyses,we proposed that COD4 might be involved in the cell wall chitin degradation during hyphal growth.