CONIOTHYRIUM MINITANS .BETA.-(1,3) EXOGLUCANASE GENE CBEG1

摘要

The invention provides the nucleotide sequence of a novel .beta.-(1,3) exoglucanase gene denoted as cbeg1 of the soil-borne fungus Coniothyrium minitans. The deduced amino acid sequence of the encoded .beta.-(1,3) exoglucanase enzyme, denoted Cbeg1, is also provided. Encoded .beta.-(1,3) exoglucanase Cbeg1 is specific for the substrate laminarin, in that results showed no activity with other substrates tested, such as carboxymethylcellulose, barley .beta.-glucan, lichenan, oat spelt xylan and birchwood xylan. The pH and temperature optima for exoglucanase Cbeg1 are 6.0 and 57.beta.C, respectively. Cbeg1 contains 784 amino acids, and has a predicted isoelectric point (pI) of 6.0 and molecular weight of 83,646 Daltons. The invention further provides vectors and cells comprising a nucleic acid molecule encoding the cbeg1 gene, and methods for producing .beta.-(1,3) exoglucanase Cbeg1. The cbeg1 gene is compatible with a eukaryotic heterologous expression system, making it particularly useful for a wide range of industrial applications, such as improvement of plant resistance to fungal phytopathogens or use in ruminant microbial transgenic strategies to improve feed digestion and nutritive carbohydrate availability from forage feed. In addition, the high activity of Cbeg1 over broad pH and temperature ranges may be beneficial for use in high temperature industrial applications, such as bleaching of pulp, which require temperatures greater than 37°C. Further, Cbeg1 may complement degradation initiated by endoglucanases which release oligoglucans, in that .beta.-(1,3) exoglucanase sequentially hydrolyzes .beta.-(1,3) glucan fragments and is required to hydrolyze oligoglucan fragments completely to obtain D-glucose, which can be assimilated.