ENZYMES OR FERMENTS 73 



6. They are inhibited by the action of antiseptics and disinfectants 

 kindred bodies. This statement is true for the enzymes found 



in the body, but not for all enzymes. 



7. They are carried down from solution by flocculent precipitates. 

 For this reason it is difficult to say whether enzymes are protein in 

 nature or only carried down by the precipitated protein. Most enzymes 

 are apparently closely associated with protein, although it is claimed 

 that some have been prepared which do not give the protein tests. 

 They are colloidal in nature and indiffusible, and readily taken up by 

 finely divided substances, such as kaolin, alumin, etc. In general 

 they are soluble in dilute glycerine, sodium chloride solution, and 

 dilute alcohol and water. 



8. (a) They are precipitated from solution by alcohol and am- 

 monium sulphate. 



(b) The precipitate on redissolving in water again manifests 

 enzymic characteristics. These facts (6, 7, 8) show the intimate 

 relationship that enzymes bear to other products of cell activity e.g., 

 bacterial toxins, hsemolysins, arid such bodies. 



9. By the presence of an enzyme a chemical action is accelerated 

 without the enzyme itself being used up in the final reaction. One 

 part of invertase can hydrolyze 100,000 parts of cane-sugar; one part 

 of rennin acts on 200,000 parts of caseinogen. It is not possible to 

 say whether an enzyme combines in any intermediate stage of the 

 reaction. This is sometimes the case in other forms of catalytic 

 action. 



10. It was originally believed that the rate of action of enzymic 

 activity was proportional to the square root of the amount of 

 enzyme present. Recent investigations with more delicate methods 

 tend to show that for most enzymes the intensity of action is 

 almost directly proportional to the concentration of enzyme 

 present. 



11. The action of an enzyme may be hindered or stopped by the 

 presence of a body known as an anti-enzyme. The exact manner in 

 which these work is not sufficiently well known. Anti-rennin may be 

 produced in the blood by the injection of rennin. The alimentary 

 tract is believed to contain anti-enzymes which prevent the digestive 

 enzyme from attacking it. Intestinal worms also contain anti- 

 enzymes for the usual ferments of the digestive tract. Administra- 

 tion of an enzyme for which the worms (e.g., tape -worms) have 

 no anti-enzyme (e.g., papain) brings about, their partial diges- 

 tion, so that their removal from the body by a purge then becomes 

 easy. 



All the above-mentioned enzymes belong to a class the mode of 

 action of which is hydrolytic. Besides these there exists in the body 

 a group of enzymes, " the oxidases," which plays a great part in the 

 oxidative processes of the body. These are generally divided into 

 two groups : the primary, or direct oxidases, which can transfer oxygen 

 directly to other bodies; the indirect, or peroxidases, which transfer 

 oxygen only in the presence of a peroxide, from which they set the 



