“…The possibility of a conformational change in the active site of ficin in the presence of substrate (Holloway et al, 1964) and proflavin (Hollaway, 1968) has been suggested. Carty and Kirschenbaum (1964) reported that hippuric acid enhanced the rate of heat denaturation of nonactivated papain. Perhaps this labilization of enzyme in the presence of hippuric acid is due to a conformational change caused by binding of the ligand.…”