60 ENZYMES 



known that are more susceptible to antiseptics than are the cells that 

 contain tliein. Formaldehyde is very destructive to enzymes, even 

 when dilute. The efifect of protein-coag-ulatiu^ antiseptics upon en- 

 zymes is, of course, greatly modified by tlie amount of protein sub- 

 stances mingled with the enzymes; and the effects of heat and other 

 injurious influences are greatly decreased by the presence of proteins 

 and other impurities. 



All enzymes are most active between 35° and 45° C, and it is inter- 

 esting to note that Kobert found this equally true for enzymes derived 

 from cold-blooded.animals. Although enzymes can stand temperatures 

 of 100°' C. or more when dry, in water they are generally destroyed 

 somewhat below 70° C. Low temperature, even — 190° C, (liquid 

 air), does not destroy them. The loss of power through heating 

 occurs gradually, and there is no sharp line at which their action 

 disappears. Sunlight is harmful to enzymes in solution, but only in 

 the presence of oxygen ; this effect is augmented by the presence of 

 fluorescent substances. Nascent oxygen is destructive to enzymes.^** 

 Radium and a:;-rays seem to have a deleterious effect upon most en- 

 zymes, and retard their rate of action; but apparently, autolytic en- 

 zymes (Neuberg^") and tyrosinase (Willcock^") are not injured by 

 these agencies.^*"* Ultra violet rays are also injurious to enzymes,^^ 

 and they can be destroyed by violent shaking (Shaklee and INIeltzer ^^). 

 Labile as enzymes are, their persistence when diy is remarkable ; 

 Kobert found active trypsin in the bodies of spiders that had been in 

 the Nuremberg ]\Iuseum for 150 years, and Sehrt ^^ found that the 

 muscle tissue of mummies contained active glycolytic ferment. 



All enzymes as ordinarily prepared have the property of decom- 

 posing hydrogen peroxide, a property possessed by substances of 

 varied nature ; this effect is prevented by CNIT, wOiich does not pre- 

 vent other enzyme manifestations, indicating that this property is due 

 to an associated enzyme, catalase. 



The retardation of enzyme action by aecuinuhitioii oi" the products 

 of their action is simply explained as being due to establislnnent of 

 o((uilibrium ; in some instancies, however, tlie substances jiroduced are 

 of themselves harmful to tlie enzymes, c. r/., alcohol and acetic acid. 



Activation of Enzymes. — AVithin the cell, the enzymes — at least those 

 1hat are excreted, sncli as trypsin and pejisin — exist with few excep- 

 tions ill ;iii active form, the z]iu\()()cu. Tlieir activation a|)pears to 

 take i)lace normally only after they have been discharged from the 



34a See Buifje. Anicr. Jour. I'livsiol, 1014 (34). 140. 



i--Ecr]. klin. Wocli., in()4 (41), lOSl. 



in Jour, of Pliysiol., lOOG (.34), 207. 



i'!ar;ii(lz('ii1 (Zcil. Siriililoiitlicr.. 1914 (4). (KKI) denies lliiil rndium nets on 

 ciizyiiies. 



1" Ajriillidii. Ann. Inst, rusteur, lill-J (1^(1). .'iS ; Hiir^'e i / <(/., Anier. .lour. 

 PliVBiol.. l!)lt) (40), 42(i. 



i"s Ainer. .T<mr. Plivsiol., 1!I0!1 (25), SI. 



1^' Meil. klin. Wdcii.. I'.MII (111, 11)7. 



