THE ENZYMIC HYDROLYSIS OF PHLORIDZIN.
1. Considering previously published data on the velocity of hydrolysis of glucosides by acids, it is shown that phloridzin, judged from the standpoint of the velocity coefficient and the critical increment for hydrolysis, resembles the gamma-fructosides (sucrose, raffinose and melezitose) more closely than it does the normal glucosides (salicin, arbutin, maltose, etc.). 2. Previous work on the enzymic hydrolysis of phloridzin shows that it is not hydrolysed by emulsin, but that it is hydrolysed by some other enzyme which occurs fairly freely in nature. 3. The difficulty in examining the enzymic hydrolysis of phloridzin lies in its very low solubility. It has been shown, in confirmation of earlier work, that emulsin is definitely without action on phloridzin at various values of pH and of temperature. This result is difficult to reconcile with the beta-glucosidic character commonly ascribed to phloridzin, and with the fact that emulsin hydrolyses (synthetic) phloroglucinol-beta-glucoside, of which phlorizin is regarded as a derivative. 4. Phloridzin is hydrolysed by a yeast maltase preparation, known to contain saccharase. Phloridzin is readily attacked by maltase-free saccharase at 30 degrees C. and pH of 4.45. If the alpha-glucase of the sucrose-splitting enzyme is (as stated) inactive under these conditions, then the enzyme responsible for the hydrolysis of phloridzin is beta-(gamma) fructosidase. 5. The sugar prepared from phloridzin differs from glucose in its specific rotation and in its action towards Bacillus pestis.
Moelwyn-Hughes
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Muspratt Laboratory of Physical and Electro-Chemistry, University of Liverpool, Liverpool, England.