The action of enzymes on hexosephosphate

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Abstract
According to the theory advanced by Harden and Young,* the presence of phosphate is essential for the alcoholic fermentation of sugar by yeast-juice. In the presence of the fermenting complex, the phosphate and sugar react together, with the simultaneous production of equivalent quantities of carbon dioxide, alcohol, and hexosephosphate. The hexosephosphate is then hydrolysed by an enzyme present in yeast-juice, with formation of a hexose and free phosphate, and the latter then again undergoes the first reaction with more sugar. The phosphate thus repeatedly passes through a cycle which may be represented by the following equations:— (1) 2C 6 H 12 O 6 + 2R 2 HP O 4 = 2CO 2 + 2C 2 H 6 O + C 6 H 10 O 4 (PO 4 R 2 )2 + 2H 2 O, (2) C 6 H 10 O 4 (PO 4 R 2 )2+ 2H 2 O = C 6 H 12 O 6 + 2R 2 HPO 4 . The normal rate of fermentation of excess of sugar by active yeast-juice is therefore dependent upon the rate at which phosphate is set free from the hexosephosphate, and any acceleration of this reaction would increase the rate of fermentation of the sugar. Thus the addition to yeast-juice and sugar of a hexosephosphatase, that is, an enzyme capable of hydrolysing hexosephosphate, would be expected to bring about this result, and the following experiments on the action of various enzyme preparations on sodium hexosephosphate have been carried out primarily with the object of finding such an enzyme.

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