Fermentation |Zymase |Glucose, etc.|Alcohol and |Yeasts enzymes | | |CO_{2} | | | | | |Lactic acid|Fatty acids |Lactic acid |Bacteria |ferment | | | | | | | |Butyric |Fatty acids |Butyric acid |Bacteria |acid | | | |ferment | | | | | | | ---------------------+-----------+-------------+-------------+---------- The above list includes only the more common and best-known plant enzymes. It seems reasonable to suppose that for every individual type of organic compound which may occur in general plant groups, or even in single species, there is a corresponding enzyme available to affect its physiological alterations. Indeed, new preparations of active enzymes from special types of plants and new evidences of the existence of enzymes in various plant organisms are continuously being reported. A few of the most common specific representatives of individual groups of enzymes may be briefly described, as follows: =Amylase= (or =diastase=, as it was first named and is still commonly called) is probably the most widely distributed enzyme of plants. It is found in practically all bacteria and fungi; in practically all seeds (it has been found in active form in seeds which were known to be over fifty years old); in all roots and tubers; and in practically all leaves, where it is located in the stroma of the chloroplasts. It appears to exist in two modifications, known, respectively, as (_a_) translocation diastase and (_b_) diastase of secretion. The first form is found in the cells of ungerminated seeds, in leaves, shoots, etc. It remains in the cells where reserve starch is stored and aids in the transformation of starch into soluble materials for translocation from cell to cell. It is active at a lower temperature than the second form, its optimum temperature being 45° to 50°. The second form is secreted by the scutellum, and perhaps by the aleurone cells, of germinating seeds, being produced by special glandular tissue. It aids in the hydrolysis of the starch for the use of the growing embryo. Its optimum temperature is 50° to 55°. The activity of amylase is accelerated by the presence of small quantities of neutral salts, especially by sodium chloride and disodium phosphate. It acts best in neutral solutions, its activity being inhibited, although the enzyme itself is not destroyed, by the presence of more than minute traces of free mineral acid or alkali.