Task: Named Entity Recognition
Input (English):  However , in a variation of this assay in which the protease is omitted , the mutant enzymes exhibited substantial levels of prolyl isomerase activity ( 5 - 20 % of wild - type ) , revealing that these mutations confer sensitivity to protease digestion and that the classic in vitro assay for prolyl isomerase activity may be misleading .
Output (English): prolyl isomerase