The physiology of the amino acids / by Frank P. Underhill.

  • Frank Pell Underhill
Date:
1915
Catalogue details

Licence: In copyright

Credit: The physiology of the amino acids / by Frank P. Underhill. Source: Wellcome Collection.

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    the transformation of these substances into amino acids—in other words, amino acid synthesis occurs. Particular attention has been paid to the deter- mination of the value of asparagine as a source of nitrogen, one of the first investigators being Mer- cadente, who believed that protein formation could take place from asparagine, especially in plants. Sachse believed that protein was formed from aspara- gine by the simple addition of fatty aldehydes. On the other hand, Loewi thought that in the presence of carbohydrates protein was formed from asparagine by a series of condensations. Zuntz suggested that in herbivora asparagine was built up into protein by bacteria in the intestine previous to utilization. This latter view has been supported by numerous investi- gators, some of whom state that protein-forming bac- teria are widely distributed in nature and may act very efficiently and quickly when in suitable envi- ronment. The evidence available seems to speak strongly in favor of the view that asparagine may serve as source of nitrogen or act at least as a protein sparer, as much as two-thirds of the protein in the diet of herbivora being replaceable by asparagine. On the other hand, several investigators claim that aspara- gine cannot take the place of protein at all, hence, cannot be used as a source of nitrogen and that even the degree of protein sparing action that may be exhibited by this amide is extremely limited. In a comparable manner it has been suggested that various ammonium salts may also replace protein to