1.4.1.13 6.4 9 at pH 6.4 and 9.0 about 50% of activity maximum 391438 1.4.1.13 6.5 8.7 at pH 6.5 and 8.7 about 50% of activity maximum 391438 1.4.1.13 7.4 9.1 at pH 7.4 and 9.1 about 50% of activity maximum 391458 1.4.1.13 8 9 - 391448