ESTIMATION AND ENZYME KINETICS OF CATALASE 411 



described by the two formulas: 



-dC = kECdt and - dE = k'CEdt 

 where (' and E are the concentrations of hydrogen peroxide and catalase» 

 respectively, k is the reaction constant of the hydrogen peroxide decomposi- 

 tion, and k' is that of the enzyme destruction. The mathematics of this 

 process have been worked out by Vamazaki (■3147), Xosaka i^OoU), and 

 Maximowitsch and Antonomova il-SSO) (rf. also Lemberg and Legge, 1705).* 

 The constants k and k' can thus be calculated from the data observed experi- 

 mentally. Fsually ku ( = k£o). the initial activity, is determined by graphical 

 extrapolation from the monomolecularpseudoconstantski, kj,and k, observed 

 at times /,, t •. and /, under conditions under which the destruction of the 

 enzyme plays only a small role (von Euler. Zeile). The specific activity of 

 catalase {Katalase-F dhigkeit, Kat.f.) i^^ defined as k« per gram of enzyme in 

 50 milliliters iSKil . p. .5.57), where k„ is measured in minutes and with decadic 

 logarithms. I'nfortunately Kat.f. was given by Hennichs {12JS, cf. also 718) 

 as k per gram of enzyme, although it was pointed out in a footnote that this 

 was to refer henceforth to oO ml., not to 1000 ml. This incorrect definition 

 has been perpetuated in the literature right up to date (rf. 2(')07,270-'j), and 

 has led many authors to the erroneous belief that the enzyme concentration 

 to which Kat.f. refers is grams per liter (rf., for example, 2-j70). This is of 

 importance since the activity of the enzyme per mole per .second calculated 

 on this basis is twenty times too high. Only Haldane's calculation (1008) is 

 free of this error. It is also present in most calculations on the enzyme con- 

 centration in liver and blood (inchiding those of Haldane). The use of 

 natural instead of decadic logarithms (1^82) has also led to Kat.f. values 

 which are not directly comparable with those of other authors. 



Enzyme activity. For horse liver catalase (extrapolated for a catalase free 

 from inactive bile pigment hematin catalase, cf. below), Sumner (2697) 

 found a value of Kat.f. of 60,000, Lemberg (1705) 5^2,000, and Keilin and 

 Hartree (U99) 54,000-55,000, while Agner (27) reports 80,000. The value 

 of k per milligram of hematin iron per liter (k/Fep) for horse liver catalase 

 was found by Zeile (SKKJ) to be between '■2500 and 3400. On the basis of our 

 knowledge of the composition of catalase, .\gner's value would correspond to 

 a k/Fep value of 4'250. Agner's value therefore would appear to be too high 

 to be correct. While Agner and Theorell (29) again find this high value for 

 Kat.f. of liver catalase, they now report a lower value ((55,000-70,000) for 

 erythrocyte catalase. Agner (^<S') had previously given the value of 100,000, 

 while Laskowski and Sumner (1(>57) found only 48,000 for crystalline 

 erythrocyte catalase. 



From a value 46,000 for Kat.f., which is probably about three-fourths of 

 the true value, Haldane (1098) calculated for the velocity constant of hydro- 

 gen peroxide decomposition k = '2 X 10* liter mole"' sec."' at 0° C, and for 

 the velocity constant of combination between enzyme and hydrogen peroxide 



*Recently, George (9S0u) found, in manometric studies, an initial rapid decay of the 

 enzyme activity, which is claimed to he reversible and is assumed to he due to the 

 rapid partial transformation of catalase into a less active state by hydrogen peroxide. 

 The initial rapid decay has heen confirmed by Lemberg and Foulkes (1698a) with the 

 oxidimetric technique. 



