Chapter 2
that light production is of fairly common occurrence during the oxidation of many organic compounds, provided the oxidation is carried out in the proper way. Many of these organic compounds must be oxidized by relatively strong alkali or such strong oxidizing agents as would have a very deleterious action on living cells. In 1913, Ville and Derrien, in a short note to the French Academy, "Catalyse Biochemique d'une Oxydation Luminescente," show that _lophin_ could be oxidized by vertebrate blood in the presence of H_{2}O_{2}. In the same year Dubois (1913) found that esculin, the glucoside from horse chestnut bark, would also oxidize and luminesce in presence of blood and H_{2}O_{2}. In these cases the haemoglobin of the blood acts as a catalyst, transferring oxygen from the H_{2}O_{2} to esculin or lophin and is to be compared to luciferase, except that luciferase does not require the presence of H_{2}O_{2}.
As the haemoglobin does not lose this power on boiling, whereas luciferase does, the analogy is far from perfect. Many oxygen carriers are known, however, which may be destroyed on boiling their solutions, namely, the peroxidases of plant juices. Esculin will not luminesce with peroxidase and H_{2}O_{2}, but pyrogallol or gallic acid will. If one mixes a test tube containing pyrogallol solution + H_{2}O_{2} with potato or turnip juice or almost any plant extract, a yellowish luminescence appears. The plant extract loses the power to cause such luminescence on boiling and the peroxidase will not dialyze. It is, of course, comparable to luciferase and acts on the thermostable, dialyzable pyrogallol-H_{2}O_{2} mixture, which is comparable to luciferin. Curiously enough, although many hydroxyphenol and amino-phenol compounds can be oxidized by peroxidase and H_{2}O_{2}, only pyrogallol and gallic acid will oxidize with light production. Many other oxidizers can take the place of the peroxidase. A list of these is given on page 151. No other peroxide can take the place of H_{2}O_{2} with peroxidases as oxidizers, but a few can replace H_{2}O_{2} with other oxidizers. This is brought out in Table 7.
TABLE 7
_Peroxides Giving Light with Pyrogallol and Oxidizers_
Key to column headings: [A]: Oxidizer. (Equal parts added to a mixture of M/100 pyrogallol and the peroxide) [B]: H_{2}O_{2} 3 per cent. [C]: Benzoyl hydrogen peroxide (insoluble powder) [D]: Ozonized turpentine (one drop) [E]: Na_{2}O_{2} (powder) [F]: BaO_{2} (powder) [G]: MnO_{2} (insoluble powder) [H]: PbO_{2} (insoluble powder) [I]: K persulfate M/10 [J]: Na perborate M/20 [K]: K perchlorate M/10 [L]: Quinone (insoluble crystals)
----------------------------------------------------------------------------- [A] |[B]|[C]|[D]| [E] | [F] |[G]|[H]| [I] | [J] |[K]|[L] -------------------------+-- +---+---+-----+-----+---+---+-----+-----+---+--- Turnip juice | + | - | - | - | - | - | - | - | | | - 1 percent blood extract | + | - | - |Faint| - | - | - | - | - | - | - | | | |flash| | | | | | | M 20 K_{4}Fe(CN)_{6} | + | - | - | - | - | - | - | - | - | - | - M 100 KMnO_{4} | + | - | - | - | - | - | - |Faint|Fair | - | - | | | | | | | |flash|flash| | M 10 FeCl_{3} | + | | | | | | | | - | - | M 100 CrO_{3} | + | | | | | | | | - | - | Na hypobromite | + | - | - |Faint|Faint| - | - |Fair |Fair | - | - | | | |flash|flash| | |flash|flash| | Ca hypochlorite | + | - | - | - | - | - | - |Faint|Fair | - | - | | | | | | | | |flash| | MnO_{2} | + | | | | | | | | | | Mn(OH)_{3} sol in peptone| + | | | | | | | | - | - | Colloidal Ag | + | | | | | | | | | | -------------------------+---+---+---+-----+-----+---+---+-----+-----+---+---
Our knowledge of the existence of such analogous, purely organic chemical oxidations, which proceed with light production, greatly strengthens Dubois' theory that the luciferin-luciferase reaction really represents a catalytic oxidation of similar nature. As Dubois (1914 _a_) expresses it, we are dealing in luminous organisms with "1 deg. une luminescence; 2 deg. une chemiluminescence; 3 deg. une oxyluminescence; 4 deg. une zymoluminescence.
"Ou si l'on bien admettre que les zymases sont encore quelque chose de vivant, une Biozymooxyluminescence." Perhaps it is not really necessary to admit that the enzymes are living in order that we may adequately visualize the nature of the photogenic process.
In the next chapter the properties of the three principal substances, luciferin, oxyluciferin and luciferase, will be studied more carefully.
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