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872 RESPIRATION AND OXIDATION.
With these views as basis and at the same time although independently
of each other Engler 1
and Bach 2
have developed a theory which for
the present is the one generally accepted. According to this theory,
peroxides of the hydrogen peroxide type are always formed as primary
oxidation products. The peroxides are either formed by a direct attach-
ment of oxygen with readily oxidizable substances or in consequence of a
simultaneous oxidation with other substances—in the last way, for
example, the formation of H2O2 in the oxidation of indigo-white to indigo
according to the formula:
Indigo^ +02 = Indigo +H2O2
Indigo-white
Only certain substances have the ability either directly or indirectly of
forming peroxides. Certain protein-like substances occurring especially
in the plants which have this ability, have been called oxygenases by
Bach and Chodat.3
Most of the substances which are oxidized within
the organism lose their ability to be directly oxidized. The oxidation
of such substances can, according to Bach,4
be accomplished in that the
oxygen is transported to the substance to be oxidized from the peroxide
simultaneously present by means of special enzymes, the peroxidases.
These latter were first prepared from pumpkins and from horse-radish
roots. In the absence of peroxides or oxygenases the peroxidases are
without action. Chodat and Bach 5 have also found that certain
preparations, which have previously been called oxidases, can be decom-
posed into oxygenases and peroxidases. According to Bach’s theory the
formation of peroxides is a constant process going on in the organism,
to which the organism accommodates itself, in that the cells by means of
the peroxidases can make use of the peroxides for the oxidation processes.
Besides this the organism also forms other enzymes, the so-called
catalases, which have the ability of decomposing the peroxides with the
formation of molecular oxygen (O2) and in this way making a possible
excess of peroxides harmless.6
In reference to the behavior of the perox-
1
Verh. naturw. Verein, Karlsruhe, 20, XI (1896), Bd. 13, 72; see also Zeitschr.
f. physiol. Chem., 59, 327 (1909).
2
Compt. Rend., 124, 951 (1897); see also Bioch. Centralbl., 1, 417, and 457 (1903);
9, 1 (1909).
a
Ber. d. d. chem. Gesellsch., 36, 600 (1903).
*Ibid., 36, 600 (1903).
5
Ibid., 36, 606 (1903).
« Bioch. Centralbl., 1, 460.
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