Pepsin Activity Peptone

Remarks. — i. The dissolving and peptonizing powers of pepsin are always fouud in all the active prq>arations these two properties are ordinarily shown with an equal intensity, a product which liquefies rapidly having also the faculty of peptonizing in a short time. However, this rule is not general. We shall see, in fact, that the conditions which favor the manifestation of one of the properties are not always those which favor the manifestation of the other, and that, furthermore, in the pepsins secreted by bacteria or molds, we find cases where the two properties do.not occur on an equal footing. 

Action of Salts, Antiseptics, Alkaloids and of Other Organic Substances.—In the action of inorganic salts on peptonization, different factors must be considered. Certain salts precipitate albumin in great quantities but even before the quantity used is sufficient to produce predpitation, these already exert an effect on the albuminoid by changing its sensitiveness towards the proteolytic enzyme. The influence of the salts on the digestion is exerted in this case by an indirect method. It is not that the pepsin has been retarded, but rather that the protein substance has become less susceptible. Thus it is that in the presence of certain quantities of NaCl, pepsin with difficulty digests albumin, but a solution of pepsin with addition of sea salt appears very active after dialysis. 

The Danilewsky reaction is studied in the following manner. In reaction tubes pour 10 c.c. of a 40 per cent peptone solution, acidified with 0.7 per cent HCl. Add a quantity of enzyme, pepsin or rennet, corresponding to 3 per cent of the quantity of peptone used, and keep the tubes in a water-bath at 65°. According to the quality of the peptone used, the liquid becomes gelatinous, curdles, or becomes turbid, in consequence of the formation of an abundant precipitate in a viscous mass.. The liquid, diluted with water, leaves on the filter a precipitate, soluble in acid or alkali. The velocity of the reaction depends primarily on the activity of the enzyme used, on the reaction, and the other conditions of medium. 

The first data on the enzymes of the pancreatic juice were furnished by Cl. Bernard in 1855 and Corvisart in 1858. It is to the latter that we owe the name of pancreatin, given to the active constituents of the pancreatic juice. Danilewsky, in 1862, isolated from a maceration of pancreas three enzymes, one amylolytic, a second proteolytic, and finally a third, capable of emulsifying and of saponifying fatty substances. Kiihnc, in 1867, first drew attention to the difference which exists between the chemical action of pepsin and that of the pancreatic enzyme. He showed the production, in this second action, of tyrosin and leucin, and also of those ill-defined residues from the hydrolysis of albuminoids which he called anti-peptones. He then characterized this proteolytic enzyme as a new enzyme, distinct from pepsin, and gave to it the name of trypsin. 

The transformation of curd into cheese is accomplished by the influence of various enzymes (i) galactase, a special trypsin, secreted by the mammary glamd simultaneously with the milk, an active substance of which we have previously had occasion to speak (2) pepsin, which is always found associated with rermet and which some writers even confound with it (3) various tryptases, or caseases, secreted by molds, bacteria, yeasts, etc., which develop on the surface or in the interior of the mass. To these enzymes, which dissolve casein and bring it to the simpler state of peptones, amino-acids, and ammonia, it is proper to add (4) amidases, that produce the formation of volatile acids (5) lactase and lactacidase, enzymes secreted by lactic bacilli, and which transform lactose into glucose and then into lactic add (6) lipases, which apparently decompose a part of the fatty material (7) finally oxidases, which bum the organic wastes, especially the adds. 

---