Note 6 — Chapter V · PATHOLOGY OF GOUT—PROTEIN METABOLISM

According to Fischer the protein molecule can be split up into amino-acids, di-amino-acids, aromatic-amino-acids, nitrogenous derivatives of the benzene ring, pyrimidine bases, pyrrolidine derivatives, cystin, and ammonia. During proteolysis the amino-acids exist in groups, e.g., glycine and leucine (glycyl-leucine), two leucine radicles (alanyl-leucine), etc.—which combinations Fischer termed polypeptides, and some of which he has been able to produce synthetically. Furthermore, Fischer proved that nitrogen equilibrium can be maintained in animals by feeding them upon these polypeptide products of proteolytic digestion which no longer gives the biuret reaction. The derivation of amino-acids, etc., from peptone is the outcome of the action of a special intestinal ferment—erepsin. This enzyme is found not only in the alimentary tract, but in all tissues of the body, its action being especially developed in the renal tissues.