Contribution of salt bridges to alkaliphily of Bacillus alkaline xylanase.

Xylanase J (XynJ) from alkaliphilic Bacillussp. strain 41M-1 is an alkaline xylanase. Structure comparison indicated that there were several specific salt bridges in the catalytic cleft of XynJ compared with neutral xylanases. Mutant enzymes were prepared by substituting several amino acids comprising the salt bridges. Some mutants exhibited acidophilic shift in optimum pH, whereas another showed alkaliphilic shift. These results suggested that the characteristic salt bridges could contribute to the alkaliphily of XynJ.