Practical physiological chemistry; a book designed for use in courses in practical physiological chemistry in schools of medicine and of science . ig. 22. Phenylalanine, C6H6CH2-CH(NHo) COOH.—This product is ^- phenyl-a-amino-propionic acid, and may be represented graphically as follows: H NH2 I IC—C—COOH. H H 74 PHYSIOLOGICAL CHEMISTRY The levo-rotatory form is obtained from proteins. Phenylalanine hasbeen obtained from all the proteins examined except from the pro-tamines and some of the albuminoids. The yield of this body from thedecomposition of proteins is frequently greater than the yiel
Practical physiological chemistry; a book designed for use in courses in practical physiological chemistry in schools of medicine and of science . ig. 22. Phenylalanine, C6H6CH2-CH(NHo) COOH.—This product is ^- phenyl-a-amino-propionic acid, and may be represented graphically as follows: H NH2 I IC—C—COOH. H H 74 PHYSIOLOGICAL CHEMISTRY The levo-rotatory form is obtained from proteins. Phenylalanine hasbeen obtained from all the proteins examined except from the pro-tamines and some of the albuminoids. The yield of this body from thedecomposition of proteins is frequently greater than the yield of crystalline form of phenylalanine is shown in Fig. 23. Tyrosine, C6H5(.OH)CH2CH(NH2)COOH.—Tyrosine, one of thefirst discovered end-products of protein decomposition, is the aminoacid, p-hydroxy-^-phenyl-a-amino-propionic acid or hydroxy phenylala-nine. It has the following formula: H NH2 C—C—COOH. H H OH The tyrosine which results from protein decomposition is usually levo-rotatory. Tyrosine is one of the end-products of tryptic digestion andusually separates in conspicuous amount early in the process of diges-. FiG. 23.—Phenylalanine. tion. It does not occur, however, as an end-product of the decomposi-tion of gelatin. Tyrosine is found in old cheese, and derives its name from this crystallizes in tufts, sheaves, or balls of fine needles, which decomposeat 295°C. and are sparingly soluble in cold (1-2454) water, but muchmore so in boiling (1-154) water. Tyrosine forms soluble salts withalkalis, ammonia, or mineral acids, and is soluble with difficulty inacetic acid. It responds to Millons reaction, thus showing the presence PROTEINS 75 of the hydroxyphenyl group, but gives no other protein test. The aro-matic groups present in tyrosine, phenylalanine, and tryptophane causeproteins to yield a positive xanthoproteic reaction. In severe cases oftyphoid fever and smallpox, in acute yellow atrophy of the liver, and in
Size: 1588px × 1574px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectbiochem, bookyear1916
