Alcoholic fermentation / by Arthur Harden.

  • Arthur Harden
Date:
1932
Catalogue details

Licence: In copyright

Credit: Alcoholic fermentation / by Arthur Harden. Source: Wellcome Collection.

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    coenzyme is the fact that although in muscle the presence of adenylic acid (adenine nucleotide) in the form of a pyrophosphate appears to be essential for the production of lactic acid it does not exert this action unless co-enzyme is also present. A co-enzyme solution free from adenylic acid can be prepared by Euler and Myrback’s method from muscle which has been allowed to autolyse at 38°. Such a preparation is quite incapable of activating the muscle enzyme unless adenylic acid pyrophosphate (which by itself is likewise inactive) is also added. The adenylic acid therefore acts as a complement to the co-enzyme. The same conditions hold for yeast preparations [Meyerhof 1930, p. 174], but apparently a smaller concentration of adenylic acid suffices than in the case of muscle. Euler and Myrback, however, were unable to confirm this [Euler, 1930, p. 17]. According to the experiments of Lohmann [1931] the factor necessary as a complement to adenylic acid or adenylic pyrophosphate is mag- nesium. The necessity for the presence of magnesium has been confirmed by Euler and Nilsson [1931], who find in agreement with Lohmann that washed dried yeast retains magnesium, which can, however, be removed by means of phosphoric acid. According to their experiments adenyl pyrophosphate + a magnesium salt produces a much smaller acceleration than is produced by co-zymase, whilst the co-zymase cannot be replaced by muscle adenylic acid. They suggest that a further activator, related to Euler’s Z factor, is also necessary. Properties of the Co-enzyme. Early observations [Buchner and Haehn, 1909] showed that digestion with potassium carbonate solution containing 2*5 grams per 100 c.c. brought about the destruction of the co-enzyme, and that this was also slowly accomplished by the repeated boiling of the juice. The co-enzyme is also destroyed both by acid and alkaline hydrolysis, and by ignition of the residue obtained when the solution is evaporated to dryness. Experiments with the purified co-enzyme [Myrback and Euler, 1924] show that in aqueous solution the decomposition by heat pro- ceeds according to a unimolecular reaction, the constant (k) at pK 5*5 and 85° being 0*26. The stability varies with the pK, and is greatest at pH 2-5, falling off rapidly at pH values above and below this. The co-enzyme is remarkably stable to oxidising agents ; it is not affected in 24 hours by a current of air at 250 at pn 4-7, and is not inactivated by bromine or KMn04 in acid solution at air temperature.
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