The enzymatic synthesis of protein. II. The effect of temperature on the synthesizing action of pepsin

In a solution of the products of the hydrolysis of protein it is theoretically possible to bring about the reverse reaction, i.e. synthesis, in two ways: by concentrating the solution, and by raising the temperature. The theoretical considerations from which the first of these conclusions was deduced have been discussed in a previous paper (1). It is sufficient to recapitulate here, that the first method is predictable from an appropriate statement of the mass law. The experimental confirmation of the prediction was described by the authors (1). The second method is predictable from certain thermodynamical considerations of reversible reactions pointed out by Moore (2). He deduced the equilibrium equation Pα, = K Pnb, where Pα, and Pb, are respectively the osmotic pressures of the substrate and its product, and K is a constant. K is a symbol for the expression P0eC/RT, where P and e are constants, R is the gas constant, C is the chemical energy involved in the breakdown of 1 gram molecule of A into n gram molecules of B, and T is the absolute temperature

The enzymatic synthesis of protein. IV. The effect of concentration on peptic synthesis

In the enzymatic hydrolysis and synthesis of proteins in vitro, the important factor, the factor upon which the direction and the degree of the reaction are dependent, is not the relative concentration of water, but the concentration of material in solution. This conclusion, pointed out by Moore, the authors have discussed at length in a previous paper (1). As shown there, the molecular concentration of water is always so enormously greater than that of the other components that the small amounts added or removed in the course of either reaction are negligible, and it may, therefore, be considered as remaining constant. The distinguishing feature of the hydrolysis and synthesis of protein is the conversion of 1 molecule of protein into a number of molecules of products. It is this characteristic which is responsible for complete hydrolysis in dilute solutions and for the ease with which synthesis is achieved in concentrated solutions. It follows that the extent of synthesis will increase as the concentration increases, and that as the concentration decreases a point will be reached at which synthesis will fail. The concentration at this point will correspond to the maximum concentration of protein capable of complete hydrolysis

The substrate in peptic synthesis of protein

Experiments are described in which it was observed that the yield of protein that can be synthesized by pepsin from a given peptic digest is highest when the hydrolyzing action of the pepsin is stopped as soon as all the protein has disappeared from the solution; and that the longer the digest is permitted to contain active enzyme the more the yield diminishes. 2. Exposure of the digest to a hydrogen ion concentration of pH 1.6 in the absence of active enzyme, does not cause a diminution in the amount of protein which can be synthesized from that digest. 3. Synthesis can be effected also in concentrated solutions of isolated fractions of a peptic digest, i.e. of proteose and of peptone. The yields are approximately the same as in similar concentrations of the whole digest, though the proteins so synthesized differ in some respects from those obtained from the whole digest. 4. The cessation of synthesis in any one digest is due to the attainment of equilibrium and not to the complete utilization of available synthesizeable material. The amount of the equilibrium yield, on the other hand, is dependent on the amount of synthesizeable material in the digest. 5. These observations are taken to show that the synthesizeability of a given mixture of protein cleavage products by pepsin depends upon its possession of a special complex in these products. This complex appears as a result of the primary hydrolysis of the protein molecule by pepsin and is decomposed in the slow secondary hydrolysis which ensues as digestion is prolonged

The stages of the peptic hydrolysis of egg albumin

1. Most of the products of the peptic hydrolysis of albumin, about 85 per cent of the total N, are primary in the sense that they arise directly from the protein molecule, and undergo no further hydrolysis. 2. A slow secondary hydrolysis, involving about 15 per cent of the total N, occurs in the proteose and simpler fractions primarily split off. 3. Acid metaprotein in peptic hydrolysis arises as a result of the action of add. It is not an essential stage in the hydrolysis of undenatured albumin. 4. Acid metaprotein is hydrolyzed by pepsin more slowly under comparable conditions than undenatured albumin

A method for the fractional analysis of incomplete protein hydrolysates

The constituents of an enzymatic hydrolysate of protein can be divided according to their complexity, into six fractions; protein, metaprotein, proteose, peptone, subpeptones, and amino acids. A method for the quantitative estimation of these fractions was devised in order to secure more definite information regarding the changes occurring during hydrolysis than is obtained by the usual free amino nitrogen determinations. The method has stood the test of continued use by different workers for over a year, and has given consistently accurate results

The Enzymatic Synthesis Of Protein. V. A Note On The Synthesizing Action Of Trypsin

In extending our investigation of the enzymatic synthesis of protein to the synthesizing action of commercial trypsin (1) the findings of Henriques and Gjaldbäk (2) were reviewed. In their experiments on plastein formation by trypsin, these authors observed a curious simultaneous hydrolysis and synthesis. This observation is confirmed

Is Narcosis Due to Asphyxiation?

Jacques Loeb and Hardolf Wasteneys. Is narcosis due to asphyxiation? Reprinted from J. Biol. Chem, vol. xiv (1913): 517-523https://digitalcommons.rockefeller.edu/collection-of-reprints-loeb/1019/thumbnail.jp

The enzymatic synthesis of protein. I. The sythesizing action of pepsin

A condition in which a synthesis of protein-like material occurs, was first arranged in 1886 by Danilewski (1) who observed the formation of a precipitate when stomach extract was added to a concentrated solution of the products of peptic hydrolysis. He considered the causative agent to be an enzyme, because precipitation did not occur if the stomach extract had been previously heated to 100°C. This result was confirmed in 1895 by Okunew. Both Danilewski and Okunew concluded that the reaction involved synthesis of the products of protein decomposition into a more composite molecule approaching in complexity a native protein