CHAPTER ^ 



STUDIES ON ALKALINE PHOSPHATASE 



The localization of enzymes in particular parts of cells is one 

 of the general problems of cytochemistry which must be largely 

 solved before it will be possible to make full use of the body of 

 knowledge of enzymes which is being built up by the biochem- 

 ists. Alkaline phosphatase is a particularly favorable enzyme 

 for experimenting on possibilities in this field, since it is rather 

 resistant to experimental procedures and thus makes readily 

 accessible study of all the various artefacts which arise in the 

 cytochemistry of enzymes — with, of course, the exception of de- 

 struction of enzyme due to the sensitivity of the enzyme itself 

 to experimental procedures. 



Alkaline phosphatase is usually defined as an enzyme which 

 splits phosphate esters according to the following equation 



ROPO3H2 ^ ROH + HOP0 3 H 2 



with a pH optimum in the vicinity of 9.3. It is not specific 

 for any special group of phosphomonoesters, but, on the other 

 hand, it will hydrolyze only the monoesters. 



The first histochemical study of alkaline phosphatase was 

 published by Robison in 1923. He showed that, if a thick 

 section of hypertrophic cartilage is immersed in a solution con- 

 taining an ester of phosphoric acid and calcium, a precipitate of 

 calcium phosphate occurs in the section at sites which may be 

 revealed by staining with silver. He showed that the calcium 

 phosphate deposits are found only in those regions in which 

 primary bone formation is occurring, and he was thus able to 

 establish a close relationship between the histological occurrence 

 of alkaline phosphatase in cartilage and calcification of car- 

 tilage. 



No further advance occurred until 1939, when Gomori and 

 Takamatsu practically simultaneously published papers in 

 which they showed that the type of technique developed by 



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