On expressed yeast-cell plasma (Buchner's 'zymase') / by Allan MacFadyen, G. Harris Morris and Sydney Rowland.

  • Macfayden, Allan, 1860-1907.
Date:
[1900]
Catalogue details

Licence: In copyright

Credit: On expressed yeast-cell plasma (Buchner's 'zymase') / by Allan MacFadyen, G. Harris Morris and Sydney Rowland. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

    19/21 (page 265)
    pltism (anabolism) j and (2) a brcakijig down of this complex matei'ial into simpler products, of which carbon dioxide and alcohol are the constant and principal constituents (katabolism). May it not be that after the expression of the cell-jiuce from the cell the same series of actions continues to take place, at least for so long a time as the rapidly changing and unstable cell-juice remains in a condition ap- proximately identical with that in which it existed in the living cell ? If this hypothesis be admitted, then the varying activities of the juice are at least partly explicable, for if we designate by y the hypothetical protoplasmic constituent of the cell with which the sugar combines, then we may imagine the processes which take place in the expressed cell-juice (in which we assume y to continue to exist) to bo somewhat as follows:— (u) In the case of auto-fermeiitation the x-sugfir combination, built up during the life of the cell, continues to decompose, after the ex- pression of the juice, yielding carbon dioxide and alcohol. (h) In the case of the disappearing sugar, the formation of the y-sugar combin.ation continues to a certain point, depending on the activity of the juide, but the decomposition of this combination comes to an end before the whole of the sugar has been liberated in the form of carbon dioxide and alcohol. In the case of a very active jirice wc may imagine this process to continue until practically the whole of the combination has been decomposed. In the case of a weak juice, the building-up process takes place more rapidly than the breaking-down process, and, consequently, when the activity of y ceases, there remains an excess of sugar in the form of the y-sugar combination. We are continuing our investigations with the yeast-cell plasma, and shall hope to communicate our further results to the Society in due course. In the meantime it may be convenient to briefly summarise the results we have already obtained, which so far appear to be leading us in the direction not of an enzyme explanation of the process, but rather of a theory which refers the phenomenon to the vital activity of the yeast-cell protoplasm. (1.) The top-yeast of English breweries yields, by suitable treat- ment, a cell-juice which possesses the transient power of decomposing sugar into alcohol and carbonic acid. (2.) The amount of gas formed by an active juice is as great as, or even greater than, that found by E. Buchner. (3.) The cell-juice as prepared by us undergoes a very considerable auto-fermentation, in some instances exceeding that given by a mixture of the same juice and cane-sugar. (4.) A moderate dilution (1 : 2) with water or physiological salt solution practically stops all fermentative activity.