Abstract
It is now quite proper to speak of an "active site" or "center" in (or on) a number of hydrolytic enzymes, chymotrypsin in particular. Such sites have been clearly demonstrated and in some cases they have even been investigated in detail. We are almost persuaded that they are the actual loci of enzyme activity in nature. Whatever we think of them, we do know that they are "some peculiar arrangement of amino acids" (2 a).