... activity in the presence of Mn2þ and Mg2þreached only 6% and 15%, respectively, of the activityin the presence of Co2þ(Fig. 4A). Co2þ,Mn2þ, and Mg2þactivation constants for BLXI activity ... than for xylose, and the relative effectiveness of the three metals was the same. Occupancy rate of the M2 site necessary for activityon glucose may be higher than that for activity on xylose; ... relatively low catalytic efficiency onxylose.BLXI thermostability and inactivation characteristicsBLXI thermostability was first characterized using the holoenzyme in the presence of 1 mM CoCl2....