Overproduction and characterization of seleno-methionine xylanase T-6

The extracellular xylanase from Bacillus stearothermophilus T-6 is a thermo stable alkaline tolerant enzyme that was found to bleach pulp optimally at pH 9 and 65 degrees C, and was successfully used in a large-scale biobleach ing mill trial. In an attempt to obtain a heavy atom derivative suitable fo r complete X-ray analysis, xylanase T-6 was labeled biosynthetically with s eleno-methionine, resulting in a 'built-in' array of atoms with specific X- ray anomalous scattering signal. Optimization of growth conditions resulted in over 0.8 g of homogenous seleno-methionine xylanase T-6 per liter cultu re. The seleno-methionine enzyme was shown to be fully active and produced single crystals suitable for complete multiple wavelength anomalous diffrac tion (MAD) structural analysis. (C) 2000 Elsevier Science B.V. All rights r eserved.