Enzymes 175 



In other cases their substrate and pH requirements are such 

 that no suitable precipitation reactions have been developed 

 for their demonstration. Enzymes with pH optima around 

 the neutral point present especially great dijfficulties because, 

 on the one hand, Ca salts cannot be used efiFectively below 

 pH ±: 8.5 and, on the other hand, the Pb salts of the sub- 

 strates are not suflBciently soluble at a pH higher than ± 5. 



Alkaline Phosphatases 



Phosphatases with a pH optimum around 9 occur in most 

 organs of almost all species examined. The largest group, that 

 of the nonspecific enzyme ( s ) , will hydrolyze any monoester 

 of phosphoric acid and, in addition, nucleic acids. High 

 polymer, native desoxyribose nucleic acid is not attacked^^"^^ 

 and must be depolymerized first if intended for use as a sub- 

 strate. The rates of hydrolysis of various substrates vary over 

 a wide range, and the optimal pH also depends on the nature 

 of the substrate. As a rule, aromatic esters are hydrolyzed 

 optimally at a higher pH (9.7-10) than aliphatic ones (8.1- 

 9).^^ All enzymes of the group are activated by Mg. They are 

 inhibited by cyanide (except hexosediphosphatase,^^ which is 

 activated but cannot be demonstrated histochemically ) . 

 Cysteine is also a strong inhibitor. ^"^ 



Whether or not nonspecific alkaline phosphatase is a 



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13. Krugelis, E. J.: Genetics, 31:221, 1946. 



14. Ross, M. H., and Ely, J. O.: J. Cell. & Comp. Physiol., 34:71, 1949. 



15. King, E. J., and Delory, G. E.: Biochem. J., 33:1185, 1939. 



16. Gomori, G.: J. Biol. Chem., 184:647, 1950. 



17. Albers, H.: Ber. d. deutsch. chfem. Gesellsch., 68:1443, 1935; Hoff- 

 mann-Ostenhof, O., Moser, H., and Putz, E.: Experientia, 4:352, 1948. 



8; Plimmer, R. H. A.: Biochem. J., 7:43, 1913; Rapoport, S., Leva, E., and Guest, G. M.: J. Biol. 

 Chem., 139:621, 1941; Courtois, J.: Bull. Soc. chim. biol., 30:37, 1948. 



*Zeller, E. A.: Enzymes as essential components of bacterial and animal toxins. In Sumner and 

 Myrback's The enzymes I, 2:986 (New York: Academic Press, 1950). 



" Harris, D. L.: J. Biol. Chem., 165:541, 1946; Feinstein, R. N., and Volk, M. E.: J. Biol. Chem,, 

 177:339, 1949. 



V Neuberg, C, and Fischer, H. A.: Enzymologia, 2: 191, 241, 360, 1937-38; Frankenthal, L., Rob- 

 erts, J. S., and Neuberg, C: Exper. Med. & Surg., 1:386, 1944. 



w Ichihara, M.: J. Biochem. (Japan), 18:87, 1933; Bredereck, H., and Geyer, E.: Ztschr. f. physiol. 

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