The simpler natural bases / by George Barger.

  • George Barger
Date:
1914
Catalogue details

Licence: Public Domain Mark

Credit: The simpler natural bases / by George Barger. Source: Wellcome Collection.

    19/232 page 7
    CHAPTER I. AMINES DERIVED FROM PROTEIN. The Putrefactive Decomposition of Amino-acids. Both animals and plants decompose proteins into their constituent amino-acids; the hydrolysis by trypsin and by erepsin in animals is similar to the formation of amino-acids in germinating seeds, which has been studied especially by Schulze and his pupils. The hydrolysis of proteins into their constituent amino-acids is also the first stage of putrefaction, but bacteria (and other fungi) are peculiar in being able to break down the amino-acids themselves into bases and acids which in general have not been demonstrated as products of the metabolism of animals and the higher plants. This degradation may take place in two ways : either an amino- group may be eliminated (deaminization) or a carboxyl-group may be removed (decarboxylation); various modifications and combinations of these two processes are possible. Little is known about the conditions determining which process takes place; generally the two go on simultaneously and deaminization preponderates. Ackermann who has carried out a number of experiments on the bacterial decarboxy¬ lation of pure amino-acids, finds that this process is favoured by the addition of peptone which serves as a source of nitrogen and in this way lessens deaminization. An organism which decarboxylates histi¬ dine has been isolated by Mellanby and Twort [1912]. Berthelot and Bertrand [1912, 1,2; 1913, 1,2; Bertrand and Berthelot, 1913] have described a similar organism from the human intestine, Bacillus aminophilus intestinalis, which decarboxylates histidine, tyrosine, tryp¬ tophane, etc. The various amines dealt with in the present chapter are ail deriv¬ able from monobasic amino-acids by decarboxylation, and it is therefore with this process that we are more particularly concerned. Decar¬ boxylation may take place by the simple removal of carbon dioxide: R R CHNH2 = CHa. NH2 + C02.
    digitised image 1
    digitised image 2
    digitised image 3