Overexpression of the Bacillus subtilis and circulans Xylanases in Escherichia coli

Complete measurement of the pKavalues of the carboxyl and imidazole groups inBacillus circulansxylanase

“…Sample conditions were 25 mM sodium phosphate, 3 mM NaN3, and 10% D20/ 90% Hz0 at 25 "C, and pH readings are uncorrected for the glass isotope effect. The labeled protein was prepared by expressing the gene encoding BCX in the Escherichia coli strain EA1 grown in a synthetic medium containing 250 mg/mL 99% ~-[y-'~C]aspartate (Muchmore et al, 1989;Sung et al, 1993). With lesions in the AsnA and AsnB genes, this strain does not convert metabolically aspartic acid to asparagine (Anderson et al, 1993).…”

Thermostabilization of Bacillus circulans xylanase: Computational optimization of unstable residues based on thermal fluctuation analysis

“…An alanine mutation at this site led to a dramatic decrease in the substrate-binding affinity of xylan (Ludwiczek et al, 2007). The gene encoding Bcx is identical to that of Bsx except at the 147 site, where a threonine for Bcx and a serine for Bsx are encoded, and both xylanases have the same specific activity toward xylan substrates (Sung et al, 1993). The modeled structure of our quadruple mutant can be superimposed onto the structure of Bsx with xylo-oligosaccharides (pdb code: 2qz3) (Fig.…”

Abnormally High pKa of an Active‐Site Glutamic Acid Residue in Bacillus Circulans Xylanase

“…Wild-type xylanase and its variants were purified according to the procedure described by Sung et al [12], with the exception that an ionexchange POROS HSII perfusion column (Perspetive Biosystems, Inc.) was used in this study. Measurements of the enzymic activity were based on the reaction of reducing sugars with hydroxybenzoic acid hydrazide reagent [13].…”