Zymase (also known as alcoholase) is an obsolete term for an

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

complex that catalyzes the

fermentation Fermentation is a type of anaerobic metabolism which harnesses the redox potential of the reactants to make adenosine triphosphate (ATP) and organic end products. Organic molecules, such as glucose or other sugars, are catabolized and reduce ...

sugar Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose Glucose is a sugar with the Chemical formula#Molecular formula, molecul ...

into

ethanol Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound with the chemical formula . It is an Alcohol (chemistry), alcohol, with its formula also written as , or EtOH, where Et is the ps ...

and

carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...

. It occurs naturally in

yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom (biology), kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are est ...

s. Zymase activity varies among yeast strains. Zymase is also the brand name of the drug pancrelipase.

Cell-free fermentation experiment

Zymase was first isolated from the yeast cell in 1897 by a German chemist named Eduard Buchner who fermented sugar in the laboratory without living cells, leading to the 1907 Nobel Prize in Chemistry. The experiment for which Buchner won the Nobel Prize consisted of producing a cell-free extract of

cells and showing that this "press juice" could ferment sugar. This dealt yet another blow to

vitalism Vitalism is a belief that starts from the premise that "living organisms are fundamentally different from non-living entities because they contain some non-physical element or are governed by different principles than are inanimate things." Wher ...

by showing that the presence of living yeast cells was not needed for fermentation. The cell-free extract was produced by combining dry yeast cells,

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...

and

diatomaceous earth Diatomaceous earth ( ), also known as diatomite ( ), celite, or kieselguhr, is a naturally occurring, soft, siliceous rock, siliceous sedimentary rock that can be crumbled into a fine white to off-white powder. It has a particle size ranging fr ...

and then pulverizing the yeast cells with a mortar and pestle. This mixture would then become moist as the yeast cells' contents would come out of the cells. Once this step was done, the moist mixture would be put through a press and when this resulting "press juice" had

glucose Glucose is a sugar with the Chemical formula#Molecular formula, molecular formula , which is often abbreviated as Glc. It is overall the most abundant monosaccharide, a subcategory of carbohydrates. It is mainly made by plants and most algae d ...

fructose Fructose (), or fruit sugar, is a Ketose, ketonic monosaccharide, simple sugar found in many plants, where it is often bonded to glucose to form the disaccharide sucrose. It is one of the three dietary monosaccharides, along with glucose and gal ...

, or maltose added,

was seen to evolve, sometimes for days. Microscopic investigation revealed no living yeast cells in the extract. Buchner hypothesized that yeast cells secrete proteins into their environment in order to ferment sugars. It was later shown that fermentation occurs inside the yeast cells. British chemist Sir Arthur Harden divided zymase into two varieties (dialyzable and nondialyzable) in 1905. Some science historians suggest that Eduard Buchner, in his 1897 work, merely repeated experiments already made by Antoine Béchamp in 1857. This is not the case: what Buchner obtained with yeast zymase, and without yeast cells, was alcoholic fermentation, while Béchamp had explicitly stated that, in absence of yeast cells, and by use of what he, also, called "zymase", he obtained only sugar inversion and no alcoholic fermentation. According to K.L. Manchester,Keith L. Manchester : "Antoine Béchamp: père de la biologie. Oui ou non?", ''Endeavour'', Vol. 25, n° 2, 1 juny 2001, pp. 68–73; Keith L. Manchester : "Louis Pasteur, fermentation, and a rival", ''South African Journal of Science'', vol. 103 (2007)
online
what Béchamp called "zymase" was invertase.

References

Enzymes