PEPTONES

PEPTONES, products of protein hydrolysis, that do not coagulate upon boiling, do not give all the reactions characteristic of proteins, and upon further hydrolysis break down into amino acids. Peptones are formed during protein digestion, during the process of autolysis, and during protein putrefaction. Unlike albumoses, peptones are not precipitated when their solutions are saturated with ammonium sulfate. Peptones are powdery substances, very soluble in water and salt solutions, partially soluble in 96% alcohol. They have a bitter taste, dialyze through animal membranes, and give a biuret reaction with a red color. They do not contain S, are not precipitated by most salts of heavy metals, many alkaloid reagents, are incompletely precipitated by tannic, phosphotungstic, phosphomolybdic acids, by a solution of mercuric iodide in potassium iodide in the presence of hydrochloric acid, by sublimate, and by absolute alcohol. Peptones are amphoteric substances (see), but with predominance of acidic properties, they give the carbamine reaction, and rotate the plane of polarization of light to the left. During peptic digestion, pepsin-peptones are obtained, for example, Kühne's amphopepton, consisting of anti- and hemipeptons (anti-peptones are difficult to further decompose, hemipeptones-easily). Histopeptones are obtained from histones; upon acid hydrolysis they give histidine, arginine, lysine, tyrosine. During tryptic digestion of proteins, anti-peptones are obtained; they are precipitated by iron-alum from a saturated (NH₄)₂SO₄ solution. When acids act on proteins, kirins are obtained, strong bases precipitated by phosphotungstic acid. Kirins give the biuret reaction, do not give the carbamine reaction, i.e., their carboxyl groups are bound, which gives them basic properties (free guanidine and amino groups).-When protamins are boiled with 10% H₂SO₄, protones are obtained, peptonoid bodies that give a biuret reaction with a red color, and rotate the plane of polarization of light to the left. Protones, called klupeons, consist of 2 molecules of arginine and 1 molecule of monoamino acid (proline, valine, alanine, serine), i.e., these are diarginyl-valine-serine, etc. (diarginyl complexes).-From ungerminated seeds of Lupinus luteus, a pepton analogous to pepsin-pepton has been isolated, C₃₂H₅₆N₈O₆, which upon acid hydrolysis gives lysine, arginine, glutamic acid. The so-called Witte pepton, obtained by digesting fibrin with artificial gastric juice, is not a pepton, but a mixture of albumoses. On the absorption of peptons-see Digestion.

I. Yaychnikov. Peptones as a nutrient medium are used in bacteriological practice; they represent a mixture of albumoses. When meat water is boiled, most of the protein coagulates and precipitates. The added pepton replaces the precipitated protein and is an important nutrient part of the broth. Commercial peptons consist of a mixture of products of complete and incomplete protein decomposition. With various methods of preparing peptons, different products of protein disintegration are obtained, and therefore in various varieties of peptons used for bacteriological purposes, higher and lower products of protein decomposition are not in the same ratios. Research on the effect of various peptons on the growth of microbes shows that depending on the pepton taken for the medium, the results obtained may also vary. Thus, for example, the same microbe forms indole or decomposes sugars with the formation of acid and gas on a medium with a pepton of one origin and does not show these signs on a medium with another pepton. There is a view that the growth of microbes, most intense on peptons obtained from deep protein decomposition, and toxin formation-better on peptons from less decomposed proteins (Walbum). Until now, two preparations of peptons have been most in use: the French Chapoteau pepton and the German Witte pepton. Later, several foreign factory-made pepton preparations appeared on the market, such as: Knoll pepton, Wulfing pepton, Riedel pepton, yeast pepton Perkam, and others. These peptons, as comparative study of them in bacteriological practice has shown, do not completely replace Witte pepton. Of non-factory-made peptons, the pepton prepared from pig stomachs according to Martin's method (see Nutrient media) deserves attention. Peptons of pancreatic digestion with the help of beef pancreas and double digestion peptons: pepsin and trypsin are also used. Media prepared with these peptons are inexpensive and, due to the presence of a large number of various products of protein disintegration, give good growth of various microbes. The pancreatic digestion gluten pepton also deserves attention. It is prepared from gluten, the protein substance of wheat flour, which is a by-product in the factory method of preparing wheat starch. It is used either fresh gluten in its raw state or its dry preparation in the form of so-called shoe glue. Of other methods of preparing peptons to replace commercial preparations, mention should be made of obtaining peptons through autolysis of brewer's yeast and hydrolysis of proteins by acids and alkalis at high temperature and pressure (see also Nutrient media).