During thermal or pH stability study, is it possible to record an increased in activity after incubation at respective temperatures or pH?
For example, incubation of enzyme without substrate to 30 - 95 oC for 2 or more hours and later perform the assay at optimum temp (50 or 60). Now in some instances, some enzymes exhibit improvement in activity, with residual activity been over 100%. Note that your reference is the highest activity obtained when performing temperature effect on enzyme activity, and that optimum temp is used in assaying post thermal stability study. Is this possible to record such increase in activity after stability test without additives?
How much over 100 %?
If it's less than 5 % I would assume the assay isn't so accurate and the enzyme is stable.
Could you be more specific, which enzyme and reaction?
One possible explanation is that your enzyme preparation contained an inhibitory substance which was destroyed by the heating, whereas the enzyme itself was stable. It is also possible for an enzyme to be activated by mild heat denaturation that releases the enzyme from a partially inhibited state that is a natural regulatory function. This is known to occur with chloroplast H+-ATPase, for example.
Before considering such possibilities, make sure the effect is reproducible.
Thank you very much. Andre the enzyme is cellulase using filter paper as a substrate. Adam, thank you for the info. I will certainly repeat the assay to see if the same results can be obtained. Thank you so much to all
One of the steps we use for thermostable enzymes during purification is to heat it till temperature it is stable in water bath. discard the unwanted precipitated protein by centrifugation . We do get increase in activity as unwanted inhibitory proteins get precipitated.