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FORMATION OF URIC ACID. 703
of different kinds act together. By means of the two deamidizing enzymes
adenase and gttanase, the adenine and guanine are transformed into
hypoxanthine and xanthine respectively, and from the latter by means
of an oxidizing enzyme, called xanthine oxidase by Burian, the uric
acid is formed. In the formation of uric acid from the nucleoproteins
we must admit of a gradual decomposition of these by the aid of different
enzymes, proteases, nucleases and deamidases. The deamidases seem
to be present in most organs, and we have numerous investigations upon
their distribution, especially those of Jones and Schittenhelm and
his collaborators.1
The distribution is not the same in all animals and
the reports regarding it are unfortunately conflicting (Schittenhelm,
Jones and Miller). We must exercise the greatest caution in drawing
conclusions as to the occurrence of these enzymes, and from experiments
made with the extracts of organs, because it seems as if also other
unknown factors must be considered in the formation of uric acid.
Thus Jones has with Rohde 2
shown that in rats the organs do not con-
tain any xanthine oxidase, and that nevertheless the urine of this animal
contains uric acid. On the other hand deamidases occur in the organs
of monkeys (and xanthine oxidase in the liver) but the urine does not
contain any uric acid and only traces of allantoin (Wells).3
The pos-
sibility of a uric acid formation in man and mammalia in another way
from the enzymotic destruction of the purines cannot, for several reasons,
be denied.
In birds the conditions are different, v. Mach 4
has shown that in
the bird family a part of the uric acid may be formed from the purine
bodies. The chief quantity of uric acid, however, is undoubtedly formed
in birds by synthesis.
The formation of uric acid in birds is increased by the administra-
tion of ammonium salts (v. Schroder), and urea acts in a similar
manner (Meyer and Jaff£). Minkowski observed, in geese with
extirpated livers, a very significant decrease in the elimination of uric
acid, while the elimination of ammonia was increased to a corresponding
degree. This indicates a participation of ammonia in the formation
of uric acid in the organism of birds; and as Minkowski has also found,
after the extirpation of the liver, that considerable amounts of lactic
acid occur in the urine, it is probable that the uric acid in birds is pro-
duced in the liver by synthesis, perhaps from lactic acid and ammonia
;
1
See footnote 4, page 703.
1
Jones, Zeitschr. f. physiol. Chem., 65, with Alice Rohde, Journ. of biol. Chem., 7;
see also Voegtlin and Jones, Zeitschr. f. physiol. Chem., 66.
3
Journ. of biol. Chem., 7.
* Arch. f. exp. Path. u. Pharm., 24.
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