LEUCIN, Ifesin (from Gk. Xeux6s, leukos, white; connected with Lat. /itx, light, Olr. 16che, lightning. OChurch Slay. ray, Skt. rue, to shine, OHG. iioht, Ger. Lieht, AS. /eoht, Eng. light), An amido-caproic acid whose chemical constitution is represented by the formula It may be obtained in the form of flat. glittering, white, odorless and tasteless crystals that are readily soluble in water and in alcohol, but prac tically insoluble in ether. Neutral aqueous solu tions of leucin usually have the power of turn ing the plane of polarized light to the left; the addition of acids or of alkalies, however, renders the solution dextro-rotatory. The leuein obtained from sources has no rotatory power at all. The importance of leucin in physiological chem istry is very considerable. It is found normally in the liver, pancreas, spleen, thymus, thyroid and salivary glands, etc. In certain diseased conditions of the liver, leuein has been found in the urine. It is one of the characteristic prod
nets of the pancreatic digestion of proteids, and it is formed wherever proteids undergo putre faction and whenever they are decomposed by acids or alkalies. According to some authors. it is largely by the transformation of leuein that urea is formed in the animal body; this has not, however, been sufficiently proved and is rather improbable. Leucin may be conrenient ly pre pared from horn-shavings by prolonged boiling with moderately dilute sulphuric acid, neutral izing with barium hydroxide, filtering,. removing the excess of barium added with a little sul acid, again filtering, and evaporating the filtrate to a small volume; the tench' then •rys tallizes out together with sonic tyrusin. but as the latter is much less soluble than the former, it may be removed by several crystallizations from water.