= KHSO, Sinigrin Allyl sulpho- Glucose Acid cyanate potassium sulphate The principal enzymes, their distribution, the substances they attack, and the chief products of their action are shown by the following table: by crushing or grinding the plant tissue, extract ing it for twenty-four hours with several vol umes of an appropriate solvent (water, salt solu tion, glycerin, weak alcohol, etc.), filtering and precipitating by the addition of an excess of al cohol or of a neutral salt. The substances thus obtained may he somewhat purified by washing, redissolving, and subjecting to a process of di alysis.
The action of i.n•yntes is probably a chemical ono, the 0.nzynic itself !wing so slowly Ile00111110Sed in the process (if it is affected al all) that it practieally acts by its mere presence. The ac tion diffcis according to the enzyme and the ubstance affected. Mostly it is one of Hydroly sis; the sabstamp acted upon takes up the The action of enzymes depends to a remarkable extent upon the temperature, the presence of free acids or alkalies, various salts, etc. Enzymes are
inactive at low temperatures (below 10° C.) and again at high temperatures (above 60° or C.). They arc destroyed at 70° to S0° C. Most of them act, best at temperatures between and 50° C. (SG° to 122° F.). It has been shown that one enzyme, is destroyed by light, particularly by blue or violet light.
The origin of those enzymes which have been investigated seems to he indirect, substances called zymogens tieing produced by the active evils. The zymogens appear as minute granules in the protoplasm which is about to form en zymes, and under appropriate conditions arc transformed into enzymes, disappearing as the enzymes increase.
The enzymes whose names are italicized in the above table are described in special articles in this encyclopaedia. Consult also Green, The Soluble Ferments and Fermentation. (New York, 1899).