Cloning, expression, and characterization of an antifungal chitinase from Leucaena leucocephala de Wit

Chitinase cDNAs from Leucaena leucocephala seedlings were cloned by PCR amplification with degenerate primers based on conserved class I chitinase sequences and cDNA library screening. Two closely related chitinase cDNAs were sequenced and inferred to encode precursor proteins of 323 (KB1) and 326 (KB2) amino acids. Expression of the KB2 chitinase from a pET32a plasmid in Origami (DE3) Escherichia coli produced high chitinase activity in the cell lysate. The recombinant thioredoxin fusion protein was purified and cleaved to yield a 32-kDa chitinase. The recombinant chitinase hydrolyzed colloidal chitin with endochitinase-type activity. It also inhibited growth of 13 of the 14 fungal strains tested.