86 MICROSCOPIC TECHNIQUES 



Moog and Steinbach (1946) have emphasized. Accordingly, differ- 

 ences in their localizations or in their properties must be exploited 

 to enable their separate identification in tissue sections (Glick, 

 1946). From the work of Dempsey and Deane (1946) it would 

 appear that several phosphatases may coexist in the same cellular 

 location, and that their differentiation must depend on differences 

 in pH optima or other properties. When glucose- 1 -phosphate is 

 employed as the substrate, enzymatic liberation of phosphate might 

 occur either by phosphatase action or by the phosphorylase action 

 which converts the substrate to glycogen or starch; accessory 

 evidence would be required to determine which of these two enzymes 

 was being visualized by the staining reaction.* 



While it does not offer rigorous proof, in some cases differentiation 

 between enzymes may be based on differences in their localization 

 as seen in stained sections. The presence in the nucleoli of the cells 

 of the wheat epicotyl of an enzyme capable of hydrolyzing adenosine 

 triphosphate, but not thiamine pyrophosphate (Glick and Fisher, 

 1946a), would suggest that these substrates are acted upon by 

 different enzymes. Likewise, the fact that a strong enzymatic 

 activity is found in the cytoplasm of cells in mouse tissues when 

 ribonucleic acid is used as the substrate, while only a slight reaction 

 is observed in the nuclei, and the reverse distribution is seen when 

 a depolymerized form of desoxyribonucleic acid is used, indicates 

 that separate enzymes are involved in the hydrolysis of these 

 substrates (Krugelis, 1946). Furthermore, the approximately equal 

 activities in both cytoplasm and nucleus toward glycerophosphate 

 as substrate might be taken as an indication of the presence of a 

 third enzyme in these cells, as Krugelis has pointed out. Another 

 example is to be found in the differences in the localizations of the 

 enzymes acting on glucose-1-phosphate and fructose diphosphate 

 when the mucosa of the mouse duodenum is studied (Dempsey and 

 Deane, 1946). Other cases might be cited to illustrate the same 

 general point. 



ZYMOHEXASE (ALDOLASE plus ISOMERASE) 



Aldolase converts hexose diphosphate to both dihydroxyacetone 

 phosphate and phosphoglyceraldehyde; isomerase catalyzes equi- 



* See Bibliography Appendix, Ref. 19. 



