Practical physiological chemistry; a book designed for use in courses in practical physiological chemistry in schools of medicine and of science . ed by Osborne and Guest^ by the hydrolysis of gliadin, theprolamin of wheat. This is the largest amount of any single decompo-sition product yet obtained from any protein except the protamines. ^ Osborne and Guest: Jour. Biol. Chcm. 9, 425, 1911. PROTEINS 83 Glutamic acid and aspartic acid arc the only dibasic acids whichhave thus far been obtained as decomposition products of proteins. Asthere is an apparent relation between the proportion of these
Practical physiological chemistry; a book designed for use in courses in practical physiological chemistry in schools of medicine and of science . ed by Osborne and Guest^ by the hydrolysis of gliadin, theprolamin of wheat. This is the largest amount of any single decompo-sition product yet obtained from any protein except the protamines. ^ Osborne and Guest: Jour. Biol. Chcm. 9, 425, 1911. PROTEINS 83 Glutamic acid and aspartic acid arc the only dibasic acids whichhave thus far been obtained as decomposition products of proteins. Asthere is an apparent relation between the proportion of these acidsand that of ammonia which the different proteins yield it is possiblethat one of the carboxyl groups of these acids is united with XHo asan amide, the other carboxyl group being united in polypeptide union(see page 32) with some other amino acid. This might be representedby the following formula: R—CHNH—COOH / CO—CHNHo—CH2—CH2— It has been shown by Thierfelder and Sherwin^ that the amide,glutamine, is a product of normal metabolism and hence this substancerather than glutamic acid is present in the protein Fig. 31.—Glutamic Acid. Reproduced from a micro-photograph made by Prof. E. T. Reichert, of the University of Pennsylvania. The glutamic acid, yielded by proteins upon hydrolysis, is dextro-rotatory. Crystals of glutamic acid are reproduced in Fig. 31. Proline, C5H9XO2.—Proline is a-pyrro\idinc-carhoxyUc acid andpossesses the following graphic structure: H2C CH2 HoC CHCnOH. NH Proline was llrst obtained as a decomposition product of casein. Pro-* Thierfelder and Sherwin: Zeil. Physiol. Chcmic, 94, 1, 1915. 84 PHYSIOLOGICAL CHEMISTRY line obtained from proteins is levo-rotatory and is the only protein de-composition product which is readily soluble in alcohol. It is also one ofthe few heterocyclic compounds obtained from proteins. Proline hasbeen found among the decomposition products of all proteins except the
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