A novel Cellvibrio mixtus family 10 xylanase that is both intracellular and expressed under non-inducing conditions.

摘要: Hydrolysis of the plant cell wall polysaccharides cellulose and xylan requires synergistic interaction a repertoire extracellular enzymes. Recently, evidence has emerged that anaerobic bacteria can synthesize high levels periplasmic xylanases which may be involved in hydrolysis small xylo-oligosaccharides absorbed by micro-organism. Cellvibrio mixtus, saprophytic aerobic soil bacterium is highly active against polysaccharides, was shown to express internal xylanase activity when cultured on media containing or glucose as sole carbon source. A genomic library C. mixtus DNA, constructed λZAPII, screened for activity. The nucleotide sequence insert from xylanase-positive clone expressed intracellular Escherichia coli revealed an ORF 1137 bp (xynC), encoding polypeptide with deduced M r 43413, defined C (XylC). Probing gene Pseudomonas fluorescens subsp. cellulosa mixtus xynC identified xynC homologue (designated xynG) XylG; XylG xynG were 67% 63% identical corresponding sequences, respectively. Both XylC exhibit extensive identity family 10 xylanases, particularly non-modular enzymes, deletion studies supported suggestion they are single-domain xylanases. Purified recombinant had 41000, displayed biochemical properties typical polysaccharidases. However, unlike previously characterized sensitive proteolytic inactivation pancreatic proteinases thermolabile. grown late-exponential phase presence cytoplasmic, envelope fractions probed anti-XylC antibodies. results showed absent culture but predominantly present periplasm cells glucose, xylan, CM-cellulose Avicel. These data suggest whose potential roles components discussed.