Highly thermostable fungal cellobiohydrolase I (Cel7A) engineered using predictive methods.

Building on our previous efforts to generate thermostable chimeric fungal cellobiohydrolase I (CBH I, also known as Cel7A) cellulases by structure-guided recombination, we used FoldX and a 'consensus' sequence approach to identify individual mutations present in the five homologous parent CBH I enzymes which further stabilize the chimeras. Using the FoldX force field, we calculated the effect on ΔG(Folding) of each candidate mutation in a number of CBH I structures and chose those predicted to be stabilizing in multiple structures. With an alignment of 41 CBH I sequences, we also used amino acid frequencies at each candidate position to calculate predicted effects on ΔG(Folding).

Combinatorial alanine substitution enables rapid optimization of cytochrome P450BM3 for selective hydroxylation of large substrates.

Combinatorial alanine substitution of active site residues in a thermostable cytochrome P450 (BM3) variant was used to generate BM3 variants with activity on large substrates. Selective hydroxylation of methoxymethylated monosaccharides, alkaloids, and steroids was thus made possible. This approach could be generally useful for improving the activity of enzymes that show only limited activity on larger substrates.

Water dynamics and salt-activation of enzymes in organic media: mechanistic implications revealed by NMR spectroscopy.

Deuterium spin relaxation was used to examine the motion of enzyme-bound water on subtilisin Carlsberg co-lyophilized with inorganic salts for activation in different organic solvents. Spectral editing was used to ensure that the relaxation times were associated with relatively mobile deuterons, which were contributed almost entirely by D(2)O rather than hydrogen-deuteron exchange on the protein. The results indicate that the timescale of motion for residual water molecules on the biocatalyst, (tau(c))(D(2)O), in hexane decreased from 65 ns (salt-free) to 0.