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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    CHAPTER VI. THE REDUCING ENZYME OF YEAST. The fact that yeast possesses powerful reducing properties has long been known, and de Rey-Pailhade [1888] showed that this reducing power was also possessed by extracts of yeast, which when brought into contact with sulphur produced an evolution of sulphuretted hydrogen. To the active substance by virtue of which this change was produced he gave the name philothion and ultimately came to regard it as a labile hydride, capable of being readily converted by the removal of the labile hydrogen atoms into a new compound, termed by him philothionogen (Pi), which in its turn readily took up hydrogen again to reproduce the original philothion (PiH2). Under the influence of Heffter’s work [1907, 1908] he regarded these labile hydrogen atoms as associated with sulphur to form -SH groups. It seems probable that the tripeptide of glutamic acid, glycine and cysteine which has been isolated by Hopkins [1921, 1929] from yeast and animal tissues, and termed glutathione, represents the philothion of de Rey-Pailhade, since it is readily oxidised to the corresponding cystine derivative, and this again is readily reduced. Its solution when shaken with sulphur yields sulphuretted hydrogen. De Rey-Pailhade apparently attributed the whole of the reducing power of yeast to the action of philothion, but it is much more probable that this substance merely acts as an acceptor for oxygen and hydrogen alternately, and that the reducing properties of the yeast are to be explained by the presence of an enzymic system. The Mode of Action of Reducing Enzymes. According to Bach’s general theory, reduction in living tissues is brought about by the aid of an enzyme (somewhat illogically termed by him perhydridase) in presence of which the elements of water are distri- buted between two substances, one, the hydrogen acceptor, being re- duced, and the other, the oxygen acceptor, being oxidised. The whole process is accordingly regarded as a “ hydrolytic oxidation-reduction ” [see Bach, 1913, 1, 2] now usually termed an oxido-reduction.
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