Enzymes 187 



adenylic acid is a 3-nucleotide ) . For histochemical purposes 

 the cheaper grades appear to be just as good as the more 

 expensive ones. 



Method 



Dissolve about 20 mg. of muscle adenylic acid in 20 ml. 

 of a 0.1-0.2 barbital or tris ( hydroxymethyl ) -aminomethane 

 buffer of pH 8.3. Add 20 ml. of a 2 per cent CaCl2 solution 

 and a few drops of a 10 per cent MgCL solution. Incubate 

 sections for 2-5 hours at 37° C. Convert Ca phosphate pre- 

 cipitate into cobalt sulfide, as in the method for alkaline 

 phosphatase. 



The reaction obtained with 5-nucleotide is more wide- 

 spread than that given by glycerophosphate or 3-nucleotides 

 and includes, in addition to the sites of activity of nonspecific 

 alkaline phosphatase, certain tracts in the central nervous 

 system and the smooth muscle of blood vessels and of the 

 urinary bladder. 



The findings appear to be compatible with the assumption 

 that, while nonspecific alkaline phosphatase will attack both 

 glycerophosphate and the two nucleotides, 5-nucleotidase 

 cannot hydrolyze substrates other than 5-nucleotide. 



Lecithinase ( Phospholipase ) 



Lecithin possesses 4 esteric linkages, and specific enzymes 

 hydrolyzing each one of the linkages have been demon- 

 strated. 



A 



H2C— i— O— OCRi 



B 

 HC— j— O— OCR2 



C D -f- 



H2C— i— OPOO— i— CH2CH2N (CH3)3 



The enzymes attacking bonds A and B belong among the 

 lipases, while those attacking bonds C and D are phospha- 

 tases or, more exactly, phosphodiesterases. For detailed in- 



