(1) When alcohol is produced for human consumption, zymase - provided by yeast - is used as the catalyst.(2) It was soon realized that the conversion of sugar into alcohol by means of yeast juice is a series of stepwise reactions, and that zymase is really a mixture of several enzymes.(3) The reaction is then carried out in presence of yeast, which contain two enzymes maltose and zymase .(4) Harden explained this by saying that a high-molecular enzyme, the zymase proper, was left on the filter, which let through a low-molecular complementary enzyme, which for the sake of brevity was called co-enzyme or co-zymase.(5) Even now the question remains open whether zymase can be added directly to the established list of enzymes.
