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SUGAR FORMATION FROM PROTEINS. 411
triiis do not raise the fat metabolism, but rather diminish it. The pro-
tein displaces a corresponding quantity of fat from the metabolism,
and if the fat were the only source of sugar then in this case we would
expect a diminished elimination of sugar instead of an increased one.
Nevertheless the above action of protein upon sugar elimination is much
more easily explained by the assumption of a sugar formation from pro-
tein than from fat.
The action of monamino-acids upon the carbohydrate metabolism
has also given important ground for the assumption cf a sugar forma-
tion from protein. That a deamidation occurs in the animal body was
shown by the earlier observations of Baumann and Blendermann.
Further proofs of this were furnished by the investigations of Neuberg
and Langstein, where in feeding experiments with alanine they found
abundance of lactic acid in the urine, and P. Mayer * observed glyceric
acid in the urine after the subcutaneous injection of diaminopropionic
acid. As from amino-acids by deamidation ketone acids or oxyacids
may be formed (see Chapter XIV) it would be of interest to test the action
of amino-acids upon the carbohydrate metabolism. Several investiga-
tions have been carried on with this in view, such as those of Langstein
and Neuberg, R. Cohn and F. Kraus, which have shown a very prob-
able formation of carbohydrate under the influence of amino-acids; but
the investigations of Embden and Salomon, and of Embden and Almagia
have positively shown, in a dog without a pancreas, that the amino-
acids can bring about a re-formation of carbohydrate. Lusk alone
and with Ringer 2
have shown the same for several amino-acids by
experiments on dogs poisoned with phlorhizin. According to the exper-
iments and calculations of the two last mentioned investigators glycocoll
and alanine can be completely transformed into glucose. Of the four
carbon atoms of aspartic acid and of the five carbon atoms of glutamic
acid three appear as glucose.
The investigations of Weinland 3
tend to prove a sugar formation
from protein He studied the formation of sugar in the chrysalis pulp
of the Calliphora and showed that the sugar formed thereby did not orig-
inate from the fat, but that the protein was the only material from
1
Baumann, Zeitschr. f. physiol. Chem., 4; Blendermann, ibid., 6; Neuberg and
Langstein, Arch. f. (Anat. u.) Physiol., 1903, Suppl.; Mayer, Zeitschr. f. phvsiol. Chem.,
42.
2
Langstein and Neuberg, 1. c; Cohn, Zeitschr. f. physiol. Chem., 28; F. Kraus,
Berl. klin. Wochenschr., 1904; Embden and Salomon, Hofmeister’s Beitrage, 5 and
6, and with Almagia, ibid., 7; Lusk, Amer. Journ. of Physiol., 22; Ringer and Lusk,
Zeitschr. f. physiol. Chem., 66.
3
Zeitsflir. f. Biol., 49 (N. F., 31); with Krummacher, ibid., 52.
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