2OO PHYSIOLOGICAL CHEMISTRY 



enzymes take part in this digestion process, one decomposing the 

 nucleic acid with formation of simple nucleotides containing a single 

 radical each of phosphoric acid, carbohydrate and base (see chapter 

 on Nucleic Acids). This enzyme may be called nucleicacidase. An- 

 other enzyme present in the intestine and intestinal juice decomposes 

 these nucleotides with the liberation of phosphoric acid. This enzyme 

 may be called nucleotidase or phosphonuclease. The intestinal mucosa 

 also decomposes many other organic phosphorus compounds with libera- 

 tion of their phosphoric acid. 1 Thus glycero-phosphoric acid and 

 hexbse-phosphoric acid as well as phosphoproteins are split in a similar 

 manner, the phosphoric acid they contain thus being absorbed in the 

 free form. 



GENERAL EXPERIMENTS ON INTESTINAL DIGESTION 



Demonstration of Enterokinase. Trypsinogen may be activated 

 by enterokinase. This activation occurs normally in the intestine. 

 Calcium salts also bring about a similar activation of the trypsinogen. 



Procedure. Prepare an extract of trypsinogen by grinding 10 grams of the 

 fresh, fat-free pancreas of the pig with a little sand. Gradually add 100 c.c. 

 of water during the grinding process. Strain through cheese cloth. 



Prepare an extract of enterokinase by grinding 5 grams of fresh, fat-free 

 duodenal mucosa 2 of the pig with a little sand. Gradually add 50 c.c. of water 

 during the grinding process. Strain through cheese cloth. 



Prepare the following series of tubes : 



(a) 10 c.c. pancreas extract +5 c.c. water. 



(b) 10 c.c. pancreas extract+5 c.c. duodenal extract. 



(c) 5 c.c. duodenal extract+io c.c. water. 



(d) 10 c.c. pancreas extract +5 c.c. duodenal extract. 



(e) 10 c.c. pancreas extract+5 c.c. duodenal extract (boiled). 



(f) 10 c.c. pancreas extract+5 c.c. of 4 per cent calcium chloride. 



Boil the contents of tube (d) for five minutes and cool to 4OC. Keep all six tubes 

 at 40C. for 20 minutes. 



To each tube add 5 c.c. of 10 per cent sodium carbonate and mix the contents 

 thoroughly and immediately. Introduce into each tube the same quantity (size 

 of a pea) of fresh fibrin. Shake the tubes and place them at 4OC. Observe the 

 tubes frequently for one hour to note digestive changes. Tubes (b) and (f) 

 should show most rapid digestion. Why? 



EXPERIMENTS ON INTESTINAL NUCLEASES. 



i. Preparation of Intestinal Extract. Wash thoroughly 100 grams of pig's 

 intestine and run through a meat chopper several times. Introduce into a 500 

 c.c. mixing cylinder and add normal salt solution to make 500 c.c. Allow to 



l Plimmer: Biochem. /., 7, 43, 1913. 



2 The dried mucosa may be substituted if desired. 



