Alcoholic fermentation / by Arthur Harden.

  • Arthur Harden
Date:
1932
Catalogue details

Licence: In copyright

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

    71/258 page 61
    Properties of the Hexosemonophosphoric Acids. Two compounds of this composition have been described, both of which have been obtained by the aid of yeast, but which differ in their properties. The Robison Ester. The first of these, frequently termed the Robison ester, was isolated in the manner described above from the products of the fermentation of sugars by yeast-juice in the presence of phosphate. The lead, barium, and calcium salts are all readily soluble in water. The acid and its salts are dextro-rotatory, the barium salt having [a]D = + 12*5° and the free acid + 25*0°. Like hexosediphosphoric acid it is a stronger acid than phosphoric acid. The dissociation constants are given on page 54. This ester has now been conclusively shown to be a mixture con- taining an aldosemonophosphoric ester and a ketosemonophosphoric ester (both of which have been isolated (see p. 52), as well as some other, as yet unidentified, phosphoric ester or esters (see p. 53)- The properties of the constituent esters, so far as they have been ascertained [Robison and King, 1931], are given below. Aldosemonophosphoric Ester.—The reducing power of the pure barium salt to sodium hypoiodite corresponds exactly to the glucose equivalent of the hexose present, whilst towards the Hagedorn and Jensen reagent it is about 78 per cent, of the equivalent. The barium salt has [a]^ + 20-6° (c = 0-84 per cent.), + 21-2° [c — 8-4 per cent.), whilst the [a]^ of the free acid is + 4I*4°- This substance yields the same phospho-osazone as Neuberg’s monophos- phoric ester and as hexosediphosphate (p. 56). The nature of the aldose residue is shown by the fact that on oxidation with bromine a phosphogluconic acid is obtained, which is converted by the action of phosphatase into ^-gluconic acid. It has been found impossible to prepare a phosphosaccharic acid from the ester by oxidation with nitric acid, and this affords strong evidence that the phosphoric acid group is situated in position 6. This is in agreement with the results obtained by King and Morgan [1929], and King, McLaughlin and Morgan [1931], who methylated the barium salt of aldomonophosphoric acid both at room temperature and at 6o°, and found that two different methoxy-compounds were produced, both of which were mixtures of the a- and £-isomerides. That obtained at 180 was very sensitive to acid hydrolysis whereas that obtained at 6o° was much more stable.
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