Except for some of the originally studied enzymes such as pepsin, rennin, and trypsin, most enzyme names end in ase. The International Union of Biochemistry (I.U.B.) initiated standards of enzyme nomenclature which recommend that enzyme names indicate both the substrate acted upon and the type of reaction catalyzed.xcept for some of the originally studied enzymes such as pepsin, rennin, and trypsin, most enzyme names end in ase. The International Union of Biochemistry (I.U.B.) initiated standards of enzyme nomenclature which recommend that enzyme names indicate both the substrate acted upon and the type of reaction catalyzed.