ENZYMES AND THEIR ACTION 15 



(c) Potato extract + 5 drops of i per cent phenol solution. 



(d) Potato extract + 5 drops of i per cent "tri-cresol" solution. 



(e) Potato extract (boiled and cooled) + 5 drops of i per cent phenol solution. 



(f) Potato extract (boiled and cooled) + 5 drops of i per cent "tri-cresol" 

 solution. 



Shake the contents of the six tubes thoroughly. Are there any immediate 

 color changes? Place the tubes in your rack, and examine them at the next 

 laboratory exercise. 



4. Experiments with Typical Oxidase Reagents. Introduce 5 c.c. of filtered 

 potato extract into each of four test-tubes. Add oxidase reagents as follows : 



(a) Potato extract + 10 drops of guaiac solution. 1 



(b) Potato extract + 10 drops of a-naphthol solution. 2 



(c) Potato extract + 10 drops of para-phenylenediamine hydrochloride 

 solutio)n. 3 



(d Potato extract -f 5 drops of a-naphthol solution + 5 drops of para- 

 phenylenediamine hydrochloride solution -f 5 drops of 10 per cent sodium 

 carbonate (Indophenol Test). 



Shake the contents of each tube thoroughly and note immediate color 

 changes. Place the tubes in the rack and leave them undisturbed until the 

 end of the laboratory exercise. Note any changes or peculiarities in the colora- 

 ation effects, especially at the surface of the liquid. 



In tube (a) the guaiaconic acid of the guaiac resin has been oxidized 

 and formed guaiac blue. 



In tube (b) a violet coloration due to the production of di-naphthol 

 appears. The oxidase has oxidized the a-naphthol. 



In tube (c) we have a change whose chemistry is not well known. 



In tube (d) we have the production of indophenol from the a-naph- 

 thol and the para-phenylenediamine hydrochloride under the influence 

 of oxidase. The indophenol is soluble in the alkaline solution. The 

 color gradually changes from red to purple as the indophenol 

 accumulates. 



The production of the above colors does not possess any biological 

 significance. These colors simply serve to indicate that certain reac- 

 tions are taking place which occur normally in living cells, although in 

 the latter case they are of course unaccompanied by any color change. 

 Intracellular oxidase favors the utilization of oxygen by a cell, just as 

 the potato oxidase has facilitated the oxidation of the chromogens in the 

 above tests. 



VI. CATALASE 



Demonstration of Catalase. The various animal tissues as liver, 

 kidney, blood, lung, muscle and brain contain enzymes called catalases 

 which possess the property of decomposing hydrogen peroxide. Cata- 



1 Made by dissolving 0.5 gram of guaiac resin in 30 c.c. of 95 per cent alcohol. 



2 Made by dissolving i gram of a-naphthol in 100 c.c. of 95 per cent alcohol. 



3 Dissolve i gram of para-phenylene diamine hydrochloride in 100 c.c. of water. 



