Cloning, sequencing, and expression of the gene encoding the Clostridium stercorarium xylanase C in Escherichia coli

The nucleotide sequence of the Clostridium stercorarium F-9 xynC gene, enco ding a xylanase XynC, consists of 3,093 bp and encodes a 1,031-amino acids with a molecular weight of 115,322. XynC is a multidomain enzyme composed o f an N-terminal signal peptide and six domains in the following order: two thermostabilizing domains, a family 10 xylanase domain, a family IX cellulo se-binding domain, and two S-layer homologous domains. Immunological analys is indicated the presence of XynC in the culture supernatant of C. stercora rium F-9 and in the cells, most likely on the cell surface. XynC purified f rom a recombinant E. coli was highly active toward xylan and slightly activ e toward p-nitrophenyl-beta-D-xylopyranoside, p-nitrophenyl-beta-D-cellobio side, p-nitrophenyl-beta-D-glucopyranoside, and carboxymethylcellulose. Xyn C hydrolyzed xylan and xylooligosaccharides larger than xylotriose to produ ce xylose and xylobiose. This enzyme was optimally active at 85 degrees C a nd was stable up to 75 degrees C at pH 5.0 and over the pH range of 4 to 7 at 25 degrees C.