Chitinase A from Stenotrophomonas maltophilia shows transglycosylation and antifungal activities

Stenotrophomonas maltophilia chitinase (StmChiA and StmChiB) genes were cloned and expressed as soluble proteins of 70.5 and 41.6 kDa in Escherichia coli. Ni–NTA affinity purified StmChiA and StmChiB were optimally active at pH 5.0 and 7.0, respectively and exhibited broad range pH activity. StmChiA and StmChiB had an optimum temperature of 40 °C and are stable up to 50 and 40 °C, respectively. Hydrolytic activity on chitooligosaccharides indicated that StmChiA was an endo-acting enzyme releasing chitobiose and StmChiB was both exo/endo-acting enzyme with the release of GlcNAc as the final product. StmChiA showed higher preference to β-chitin and exhibited transglycosylation on even chain length tetra- and hexameric substrates. StmChiA, and not StmChiB, was active on chitinous polymers and showed antifungal activity against Fusarium oxysporum.