Purification and characterization of three chitinases and one beta-1,3-glucanase accumulating in the medium of cell suspension cultures of barley (Hordeum vulgare L.)

Three basic chitinases and one basic beta-1,3-glucanase were secreted into the medium when embryogenic cell suspensions of barley (Hordeum vulgare L.) cv. 'Igri' were cultured as undifferentiated aggregates in the presence of 2,4-D. The enzymes were purified by affinity and ion exchange chromatography. Two of the chitinases were identified as the previously described endochitinases T and C from barley grain. The third and novel chitinase, designated K, was the major basic chitinase in the medium constituting 4% of the soluble protein. Chitinase K was found to be a 33-kDa endochitinase with pI at 8.7. Further analysis showed that this enzyme is also expressed in barley grain. The amino acid composition and five partial amino acid sequences covering 93 residues of chitinase K were determined. A high similarity was found between chitinase K and barley chitinase T and C as well as basic chitinases from barley aleurone and barley, bean and potato leaves. The purified beta-1,3-glucanase with a molecular weight (MW) of 32 kDa and pI greater-than-or-equal-to 9.8 constituted 1% of the soluble protein in the medium. Based on similar MW, pI and amino acid composition as well as identical N-terminal sequence (24 residues) this enzyme was identified as the previously described beta-1,3-endoglucanase GII from germinating barley grain. The results suggest that secretion of chitinase and beta-1,3-glucanase from the embryogenic cell suspensions of barley corresponds to accumulation of the same enzymes in barley grain.