Heterologous expression and characterization of an antifungal chitinase chi39 from bacillus thuringiensis serovar konkukian

A chitinase gene from bacillus thuringiensis serovar konkukian s4 was cloned,sequenced,and heterologously expressed in escherichia coli m15. the recombinant enzyme (chi39) was purified by ni-nta affinity column chromatography. the chi39 gene was shown to contain a single open reading frame (orf) with a capacity to encode a protein with a predicted molecular mass of 39 kda and isoelectric point of 5.75. comparison of chi39 with other chitinases has shown this enzyme to contain a single n-terminal family 18 catalytic-domain. the turnover rate (kcat) of the enzyme was determined (28.3±0.70 s-1) using colloidal chitin as substrate. the purified enzyme was active at a broad range of ph (ph 4.5-8.0) and temperature (4-75 °c) with a peak activity at ph 5.0 and 60°c. however,the enzyme activity was found to be stable up to 50°c for longer incubation periods (36 h). moreover,purified enzyme was shown to inhibit fungal spore germination and hyphal growth of pathogenic fungi fusarium oxysporum and aspergillus niger. the present study will lead us to develop biocontrol agent.