DIASTASE (Cik. diastasis, sep aration, from Sitarcivat, diistanui, to separate, from old, dia, apart io-rdvat, histanai, to stand). An enzyme found in both animals and plants, which has the power of converting starch into a sugar. It has also been called amylase. and in the saliva is known as ptyalin. In plants, where it is practically universal, diastase occurs in two modifications. which have their parallels also in animals, viz, secretion diastase and translocation diastase. These differ in their distribution, their mode of action on starch grains and starch paste, the optimum tempera ture for activity, etc. Translocation diastase is the more widely distributed of the two, being formed by fungi and bacteria, and in leaves, shoots, storage organs, and pollen-grains, as well as in the seed. Its function seems to be to make possible the translocations of carbo hydrate food, temporarily or permanently stored as starch, by digesting it into a soluble sugar. Translocation diastase is therefore of the utmost importance in plant nutrition. Secretion di astase is formed by special secreting cells in the embryo of seeds, especially in grasses. and plays its chief ride in germination by making available the food stored as starch in the seed. Transloca tion diastase digests and liquefies starch paste slowly, and erodes starch-grains uniformly at the snrfaee or in the centre until they disappear. Secretion diastase liquefies starch paste rapidly and corrodes starch-grains by forming irregular pits, which, penetrating the grain in various directions, deepen and widen until it falls to pteees. Translocation diastase is most active at 45° to 50• C. (113° to 122° F.), secretion diastase at 50° to 55° C. Both are destroyed at 70° C. (]55° Diastase cannot he obtained in a pure state; and because its composition has not yet been ascertained. no test for purity can be established.
It may be obtained by crushing or grinding the tissue containing it, e. g. malt. and extracting it for twenty-four hours with three or four times its bulk of water or weak alcohol. The liquid may lie filtered off and the various. substances dissolved along with the diastase may be par tially eliminated by adding about three volumes of absolute alcohol. collecting on a filter the Pre •ipitaly washing it with absolute alcohol and etliers ant' drying. Thr powder so obtained may be still nuttier purified by solution in water, re•precipitation ttith :11,1.1101, and dialysis. 111 tie dry -talc. it may he kept indefinitely, and ictallis it- dige-tke power.
Ito. .1. lion of diastase on starch is our of htdr, Isis, ix. it the starch to combine with water and break up into simpler coin pounds. The ilitcrill•dillte steps in the process, are not knotty. llUt the ultimate products of the hydrolysis are a %ariety of sugar called maltose, so per Lent., and dextrin (q.v.), 20 per cent. Diastase act- most effectitely in a weak solution of common salt and carbonic acid, 1 .1(1..1 0: ore ordinarily present ill plant-cells. The pres ence of antiseptics. as well as of alkalies, acids, and many salts. has the etreet of greatly dimin ishing and sometimes of altogether destroying the efficacy of the enzyme.
Diastase is largely made use of in the manu facture of beer and alcohol. small quantities of the enzyme being capable of effecting the trans formation of a considerable amount of starch. _1 preparation of diastase has of late also been used with some success in the treatment of fer mentative dyspepsia. See .1i.conot.; ItErAt; DEX TRIN: ENZYMES.