PURIFICATION AND CHARACTERIZATION OF CHITINASES FROM TRANSFORMED CALLUS SUSPENSION-CULTURES OF TRICHOSANTHES KIRILOWII MAXIM

Three extracellular basic chitinases designated as TKC 15, TKC 28-I, a nd TKC 28-II were purified from Agrobacterium rhizogenes A4 transforme d Trichosanthes kirilowii Maxim. callus suspension cultures using PerS eptive HS/M cation exchange and Sephadex G 75 S gel filtration chromat ography, These chitinases exhibited maximal activity at pH 6 and tempe rature at 40-45 degrees C, N-terminal analysis suggests that two chiti nases (TKC 28-I and TKC 28-II) with indistinguishable molecular masses (28 kDa) belonged to the Class III chitinase family. Another basic pr otein with a molecular mass of 15 kDa (TKC 15) also possesses chitinas e activity, Chitobiose was the major end product from chitin digested by TKC 28-I and TKC 28-II whereas TKC 15 released a mix of tetramers, trimers and dimers from chitin, Slow cleavage of chitotriose by TKC 28 -I and 28-II and no cleavage of tetramers and trimers by TKC 15 were o bserved. TKC 28-I cleaved tetramer faster than trimers, 1.1 x 10(-4) M .h(-1).mu g(-1) and 1.5 x 10(-6) M.h(-1).mu g(-1) respectively. All ch itinases showed inhibitory ability in a cell-free protein translation system but were far less potent than trichosanthin, a ribosome inactiv ating protein, found in the storage root tuber of T. kirilowii. The pu rified T. kirilowii chitinases did not show antifungal activity agains t Aspergillus flavus or Trichoderma viride.