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LEUCINE. HI
d-valine can be obtained aa microscopic crystalline leaves. It iq
rather readily soluble in water and the solution lias a faint sweetish taste
and at the same time somewhat bitter. The solution has a rotation
of (a) D = +6.42°. The hydrochloric acid solution (20 per cent) shows,
according to Fischer, a rotation of (r;)
D =+28.8°. The copper salt,
which forms leaves which are rather soluble in water, is very easily soluble
in methyl alcohol (Schulz and Winterstein 1
).
The phenylisocvanate melts at 147°, and on boiling with 20 per cent
hydrochloric acid for a short time, it is changed into rf-phenylisopropyl
hydantoin, which melts at 131-133° C.
On putrefaction valine yields isobutylamine and isovaleric acid.
/-Leucine (aminocaproic acid, or, more correctlv, a-aminoisobutylacetic
CH3CH3
\y
CH
acid), CeHi3N02= CH2 , is produced from protein substances in
CH(NH2)
COOH
their hydrclytic cleavage by proteolytic enzymes, by boiling with dilute
acids or alkalies or by fusing with alkali hydroxides, and by putre!: ttion.
There are also observations that indicate that in the hydrolysis besides
the ordinary leucine perhaps also normal leucine may be formed (Heckel
and Samec 2
).
Because of the ease with which leucine (and tyrosine) are formed
in the decomposition of protein substances, it is difficult to decide pos-
itively wT
hether these bodies when found in the tissues are constituents
of the living body or are to be considered only as decomposition products
formed after death. Leucine, it seems, has been found as a normal
constituent of the pancreas and its secretion, in the spleen, thymus, and
lymph glands, in the thyroid gland, in the salivary glands, in the kidneys
and in the liver. It also occurs in the wool of sheep, in dirt from the
skin (inactive epidermis), and between the toes, and its decomposition
products have the disagreeable odor of the perspiration of the feet.
It is found pathologically in atheromatous cysts, ichthyosis scales, pus,
blood, liver, and urine (in diseases of the liver and in phosphorus poison-
ing). Leucine often occurs in invertebrates and also in the plant king-
dom. On hydrolytic cleavage various protein substances yield different
amounts of leucine, as shown in the tables given on pages 106, 107, 115 and
125. From the figures, there given, we call attention to the following:
Erlenmeyer and Schoffer obtained 36-45 per cent leucine from the
cervical ligament. E. Fis^ her and Abderhalden 20 per cent from haemo-
1
Zeitschr. f. physiol. Chem., 35.
2
Heckel, Monatsh. f. Chem., 29; Samec, ibid., 29.
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