Enzymes 167 



nant changes. Roskin and co-workers and Voinov^^ assert that malig- 

 nant cells (in unfixed smears) do not stain with the dye while non- 

 maHgnant ones do. Ludford^^ and the present writer^^ were unable to 

 verify Roskin's claims. 



2. HYDROLYTIC ENZYMES 



The hydrolytic enzymes demonstrable histochemically be- 

 long, with the exception of two individual enzymes— phos- 

 phamidase and glucuronidase— in the group of esterases; that 

 is, they hydrolyze esteric linkages. In modern usage the term 

 "esterase" is restricted to those enzymes with a substrate 

 specificity for carboxyhc esters. The other ester-split dug en- 

 zymes derive their names from the acid components of the 

 esters they hydrolyze preferentially, since it appears that 

 their specificity is determined by the acid moiety (phos- 

 phatase, sulfatase). 



Methods for Hydrolytic Enzymes in General 



Depending on the substrate, hydrolysis yields an acid ion 

 and an alcohol or a phenol ( or, in the case of phosphamidase, 

 an acid and an amide). Reactions have been devised for the 

 demonstration of either the acid or the alcoholic moiety. 



The acids are demonstrated by their regular precipitation 

 reactions with metal ions. Theoretically, many cations could 

 be used to trap the acid ions; in practice, however, only a 

 few are suited for histochemical apphcation, the majority 

 being too toxic to enzymes or incompatible with the sub- 

 strate at the optimal pH of the reaction. The ones most often 

 used are calcium and lead; cobalt, iron, and copper are 

 employed in one method each. . 



The principle is to add a cation, known from analytical 



Ztschr. f. Zellforsch. u. mikr. Anat., 19:150, 1933; Roskin, G., and Solow- 

 jewa, W.: Acta cancrol., 1:464, 1934-35; Roskin, G.: Bull. biol. et med. 

 exper., 3:375, 1937; Roskin, G.: Bull, d'histol. appliq. a la physiol., 15:20, 

 1938; Roskin, G., and Struve, M. E.: Stain Technol., 22:83, 1947. 



81. Voinov, V. A.: Klinicheskaia meditsina, 18:51, 1940. 



82. Ludford, R. J.: Arch. f. exper. Zellforsch., 17:339, 1935. 



83. Gomori, G.: Unpublished. 



