Part 4

COMPOSITION OF SOME OF THE MORE PROMINENT PROTEIDS OCCURRING IN NATURE.[A]

=============================================================================== Substance. | C | H | N | S | O | P | Ash.| Origin. | Author. ------------+-----+----+-----+----+-----+----+-----+-----------+--------------- Serum- |53.05|6.85|16.04|1.77|22.29| |{0.57|Serum from |Hammarsten.[54] albumin | | | | | | |{-- |horse blood| Serum- |52.25|6.65|15.88|2.27|22.95| |{1.84|Pleural |Hammarsten.[54] albumin | | | | | | | |exudation | Egg-albumin |52.25|6.90|15.25|1.93|23.67| | |Non- |Hammarsten.[54] | | | | | | | |coagulated | Egg-albumin |52.33|6.98|15.89|1.83|22.97| | 1.11|Non- |Chittenden and | | | | | | | |coagulated |Bolton.[55] Lacto- |52.19|7.18|15.77|1.73|23.13| | |Cow’s milk |Sebelien.[56] albumin | | | | | | | | | Vegetable- |52.25|6.76|16.07|1.48|23.44| | 0.70|Corn |Chittenden and albumin | | | | | | | |or maize |Osborne.[57] Vegetable- |53.02|6.84|16.80|1.28|22.06| | 0.82|Wheat |Osborne and albumin | | | | | | | | |Voorhees.[58] Proteose, |52.13|6.83|16.55|1.09|23.40| | 0.79|Hemialbu- |Kühne and animal | | | | | | | |mose, urine|Chittenden.[59] Proteose, |50.60|6.68|16.33|1.62|24.77| | 2.99|Corn |Chittenden and vegetable | | | | | | | |or maize |Osborne.[57] Proteose, |51.86|6.82|17.32| | | | 0.25|Wheat |Osborne and vegetable | | | | | | | | |Voorhees.[58] Proteose, |49.98|6.95|18.78| | | | 1.80|Flax-seed |Osborne.[60] vegetable | | | | | | | | | Proteose, |46.52|6.40|18.25| | | | 2.20|Cocoanut |Chittenden and vegetable | | | | | | | |meat |Setchell.[61] Vitellin, |51.71|6.84|18.12|0.85|22.48| | 1.20|Corn |Chittenden and spheroidal | | | | | | | |or maize |Osborne.[57] Vitellin, |51.60|6.97|18.80|1.01|21.62| | 0.30|Squash-seed|Chittenden and crystalline| | | | | | | | |Hartwell.[62] Vitellin, |51.81|6.94|18.71|1.01|21.53| | 0 |Squash-seed|Chittenden and amorphous | | | | | | | | |Hartwell.[61] Vitellin, |51.48|6.94|18.60|0.81|22.17| | 0.54|Flax-seed |Osborne.[60] crystalline| | | | | | | | | Vitellin, |51.03|6.85|18.39|0.69|23.04| | 0.49|Wheat |Osborne and spheroids | | | | | | | | |Voorhees.[58] Vitellin, |51.63|6.90|18.78|0.90|21.79| | 0.56|Hemp-seed |Chittenden and crystalline| | | | | | | | |Mendel.[61] Vitellin, |51.31|6.97|18.75|0.76|22.21| | 0.03|Castor bean|Osborne.[63] crystalline| | | | | | | | | Vitellin, |52.18|6.92|18.30|1.06|21.54| | 0.20|Brazil nut |Osborne.[63] crystalline| | | | | | | | | Vitellin, |51.23|6.90|18.40|1.06|22.41| | 0.25|Cocoanut |Chittenden and semi- | | | | | | | |meat |Setchell.[62] crystalline| | | | | | | | | Myosin, 13 |52.82|7.11|16.77|1.27|21.90| | 1.45|Muscle- |Chittenden and different | | | | | | | |tissue |Cummins.[64] samples | | | | | | | | | Myosin, |52.68|7.02|16.78|1.30|22.22| | 0.63|Corn or |Chittenden and vegetable | | | | | | | |maize |Osborne.[57] Myosin, |52.18|7.05|17.90|0.53|22.34| | 0.10|Oats |Osborne.[65] vegetable, | | | | | | | | | crystalline| | | | | | | | | Paraglobulin|52.71|7.01|15.85|1.11|23.24| | 0.30|Blood |Hammarsten.[66] | | | | | | | | of horse | Fibrinogen |52.93|6.90|16.66|1.25|22.26| | 1.75|Blood |Hammarsten.[67] | | | | | | | | of horse | Zein |55.23|7.26|16.13|0.60|20.78| | 0.43|Corn or |Chittenden and | | | | | | | |maize |Osborne.[57] Gliadin |52.72|6.86|17.66|1.14|21.62| | 0.51|Wheat |Osborne and | | | | | | | | |Voorhees.[58] Gliadin |53.01|6.91|16.43|2.26|21.39| | |Oats |Osborne.[63] | | | | | | | | | Glutenin |52.34|6.83|17.49|1.08|22.25| | |Wheat |Osborne and | | | | | | | | |Voorhees.[58] Coagulated |52.33|6.98|15.84|1.81|23.04| | 0.27|Egg-albumin|Chittenden proteid | | | | | | | | |and Bolton.[55] Coagulated |51.58|6.88|18.80|1.09|21.65| | 0.25|Vitellin, |Chittenden proteid | | | | | | | |hemp-seed |and Mendel.[61] Fibrin |52.68|6.83|16.91|1.10|22.48| | 0.56|Blood |Hammarsten.[67] | | | | | | | |of horse | Oxyhæmo- |53.85|7.32|16.17|0.39|21.84| | 0.43|Blood of |Hoppe- globin | | | | | | | Fe.|dog | Seyler.[68] Oxyhæmo- |54.71|7.38|17.43|0.48|19.60| | 0.39|Blood of |Hütner.[69] globin | | | | | | | Fe.|pig | Mucin |50.30|6.84|13.62|1.71|27.53| | 0.33|From snail |Hammarsten.[70] | | | | | | | | | Mucin |48.84|6.80|12.32|0.84|31.20| | 0.35|Submaxil- |Hammarsten.[71] | | | | | | | |liary gland| Chondro- |47.30|6.42|12.58|2.42|31.28| | |Cartilage |Mörner.[72] mucoid | | | | | | | | | Nuclein |50.60|7.60|13.18| | |1.89| |Human brain|V. Jaksch.[73] | | | | | | | | | Nuclein |49.58|7.10|15.02| | |2.28| |Pus |Hoppe- | | | | | | | | | Seyler.[74] Casein |52.96|7.05|15.65|0.71|22.78|0.84| |Cow’s milk |Hammarsten.[75] | | | | | | | | | Casein |53.30|7.07|15.91|0.82|22.03|0.87| 0.98|Cow’s milk |Chittenden and | | | | | | | | |Painter.[76] Nucleo- |48.41|7.21|16.85|0.70|24.41|2.42| |Leucocytes |Lilienfeld.[77] histon or | | | | | | | | | leuco- | | | | | | | | | nuclein | | | | | | | | | Gelatin |49.38|6.81|17.97|0.71|25.13| | 1.26|Connective |Chittenden and | | | | | | | |tissue |Solley.[78] Elastin |54.24|7.27|16.70|0.30|21.79| | 0.90|Neck-band |Chittenden | | | | | | | | |and Hart.[79] Elastin |53.95|7.03|16.67|0.38|21.97| | 0.72|Aorta |Schwarz.[80] | | | | | | | | | Keratin |49.45|6.52|16.81|4.02|23.20| | 1.01|White |Kühne and | | | | | | | |rabbit’s |Chittenden.[81] | | | | | | | |hair | Neurokeratin|56.99|7.53|13.15|1.87|20.46| | 1.35|Human brain|Kühne and | | | | | | | | |Chittenden.[82] Reticulin |52.88|6.97|15.63|1.88|22.30|0.34| 2.27|Reticular |Siegfried.[83] | | | | | | | |tissue | ------------+-----+----+-----+----+-----+----+-----+-----------+---------------

[A] Many of these results represent the average of a large number of individual analyses.

[54] Jahresbericht f. Thierchemie, Band 11, p. 19.

[55] Studies in Physiol. Chemistry, Yale Univer., vol. 2, p. 126.

[56] Zeitschr. physiol. Chem., Band 9, p. 463.

[57] Amer. Chemical Journal, vols. 13 and 14.

[58] Ibid., vol. 15, p. 379.

[59] Zeitschr. f. Biol., Band 19, p. 198.

[60] Amer. Chemical Journal, vol. 14, p. 629.

[61] Not hitherto published.

[62] Journal of Physiology, vol. 11, p. 435.

[63] Amer. Chemical Journal, vol. 14, p. 662.

[64] Studies in Physiol. Chemistry, Yale University, vol. 3, p. 115.

[65] Fourteenth Annual Report Conn. Ag. Exp. Sta., 1890; 2d paper, Amer. Chemical Journal, vol. 14, p. 212.

[66] Pflüger’s Archiv f. Physiol., Band 22, p. 489.

[67] Ibid., Band 22, p. 479.

[68] Hoppe-Seyler’s Med. Chem. Untersuch, p. 189.

[69] Hoppe-Seyler’s Chem. Analyse, 6th auflage, p. 275.

[70] Pflüger’s Archiv f. Physiol., Band 36. p. 392.

[71] Zeitschr. f. physiol. Chem., Band 12. p. 185.

[72] Jahresbericht f. Thierchemie, Band 18, p. 219.

[73] Pflüger’s Archiv f. Physiol., Band 13, p. 469.

[74] Hoppe-Seyler’s Med. Chem. Untersuch, p. 489.

[75] Zeitschr. f. physiol. Chem., Band 7, p. 269.

[76] Studies in Physiol. Chemistry, Yale University, vol. 2, p. 172.

[77] Du Bois Reymond’s Archiv f. Physiol., 1892, p. 170.

[78] Journal of Physiology, vol. 12. p. 23.

[79] Studies in Physiol. Chemistry, Yale University, vol. 3, p. 19; also Zeitschr. f. Biol., Band 25, p. 368.

[80] Zeitschr. f. physiol. Chem., Band 18, p. 491.

[81] Zeitschr. f. Biol., Band 26, p. 304.

[82] Ibid., p. 301.

[83] Jahresbericht f. Thierchemie, Band 22, p. 15.

In considering the results tabulated above, it is to be remembered that all of these bodies, with the exception of keratin, neurokeratin, and reticulin, are more or less digestible in either gastric or pancreatic juice, or indeed in both fluids. I will not take time here to point out the obvious genetic relationships and differences in composition shown by the above data, but will immediately call your attention to the fact that there are other and more important points of difference between many of these proteids which are hidden beneath the surface, and which a simple determination of composition will not bring to light. I refer to the chemical constitution of the bodies, to the way in which the individual atoms are arranged in the molecule, on which hinges more or less the general properties of the bodies and which in part determines their behavior toward the digestive enzymes, as well as toward other hydrolytic agents. These differences in inner structure can only be ascertained by a study of the decomposition products of the proteids, and of the way in which the complex molecules break down into simpler. The nature of the fragments resulting from the decomposition of a complex proteid molecule, gives at once something of an insight into the character of the molecule. Thus, egg-albumin exposed to the action of boiling dilute sulphuric acid yields, among other fragments, large quantities of leucin and tyrosin, the latter belonging to the aromatic group and containing the phenyl radical. Collagen, or gelatin, on the other hand, by similar treatment fails to yield any tyrosin or related aromatic body, but gives instead glycocoll or amido-acetic acid, in addition to leucin, lysin, and other products common to albumin. Its constitution, therefore, is evidently quite different from that of albumin, but the composition of the body reveals no sign of it. Further, we have physiological evidence of this difference in constitution in that gelatin, though containing even more nitrogen than albumin, is not able to take the place of the latter in supplying the physiological needs of the body; its food-value is of quite a different order from that of albumin.

But while all of the individual proteids show many points of difference, either in composition, constitution, reactions, or otherwise, they are nearly all alike in their tendency to undergo hydrolytic decomposition under proper conditions; the extent of the hydrolysis and accompanying cleavage being dependent simply upon the vigor or duration of the hydrolytic process.

Furthermore, all of the simple proteids, at least, give evidence of the presence of two distinct groups or radicals, which give rise by decomposition or cleavage to two distinct classes of products. These two groups, which we may assume to be characteristic of every typical proteid, Kühne has named the anti- and hemi-group respectively. This conception of the proteid molecule is one of the foundation-stones on which rest some of our present theories regarding the hydrolytic decomposition of proteids, especially by the proteolytic enzymes. Moreover, it is not a mere conception, for it has been tested so many times by experiment that it has seemingly become a fact. The two groups, or their representatives, can be separated, in part, at least, by the action of dilute sulphuric acid (three per cent.) at 100° C. Thus, after a few hours’ treatment of coagulated egg-albumin, about fifty per cent. of the proteid passes into solution, while there remains a homogeneous mass, something like silica in appearance, insoluble in dilute acid, but readily soluble in dilute solutions of sodium carbonate. This latter is the representative of the anti-group, originally named by Schützenberger[84] hemiprotein, but now called antialbumid.[85] It is only slightly digestible in gastric juice, but is readily attacked by alkaline solutions of trypsin, being converted thereby into a soluble peptone known as antipeptone. In the sulphuric acid solution, on the other hand, are found the representatives of the hemi-group; viz., albumoses, originally known as one body, hemialbumose,[86] together with more or less hemipeptone, leucin, tyrosin, etc.

[84] Recherches sur l’albumine et les matières albuminoides. Bulletin de la Société chimique de Paris, vols. 23 and 24.

[85] Kühne: Weitere Mittheilungen über Verdauungsenzyme und die Verdauung der Albumine. Verhandl. d. Naturhist. Med. Ver. zu Heidelberg, Band 1, p. 236.

[86] Kühne und Chittenden: Ueber die nächsten Spaltungsproducte der Eiweisskörper. Zeitschr. f. Biol., Band 19, p. 159.

The fact that we have so many representatives of the hemi-group in this decomposition is significant of the readiness with which the so-called hemi-group undergoes change. All of its members are prone to suffer hydration and cleavage, passing through successive stages until leucin, tyrosin, and other simple bodies are reached. These, and other similar crystalline bodies, are likewise the typical end-products of proteolysis by trypsin, and presumably come directly from the breaking-down of hemipeptone. Antipeptone, on the other hand, is incapable of further change by the proteolytic ferment trypsin. Hence, the hemi-group can be identified by the behavior of the body containing it toward trypsin; _i.e._, it will ultimately yield leucin, tyrosin, and other bodies of simple constitution to be spoken of later on. The anti-group, however, will show its presence by a certain degree of resistance to the action of trypsin, antipeptone being the final product of its transformation by this agent; _i.e._, leucin, tyrosin, etc., will not result. In this hydrolytic cleavage of proteids the anti-group does not always appear as antialbumid. It may make its appearance in the form of some related body, the exact character of the product being dependent in great part upon the nature of the hydrolytic agent, but in every case the characteristics of the anti-group will come to the surface when the body is subjected to the action of trypsin.

The above-described treatment of a coagulated proteid with water containing sulphuric acid evidently induces profound changes in the proteid molecule. The conditions are certainly such as favor hydration, and in the case of complex molecules, like the proteids, cleavage might naturally be expected to follow. Analysis of antialbumid from various sources plainly shows that its formation is accompanied by marked chemical changes. Thus, the following data, showing the composition of antialbumid formed from egg-albumin and serum-albumin by the action of dilute sulphuric acid at 100° C., gives tangible expression to the extent of this change:

=========================================================== | |Antialbumid[87]| | Antialbumid[87] | Egg- | from | Serum- | from |albumin.| egg-albumin. |albumin.| serum-albumin. --------+--------+---------------+--------+---------------- C.......| 52.33 | 53.79 | 53.05 | 54.51 H.......| 6.98 | 7.08 | 6.85 | 7.27 N.......| 15.84 | 14.55 | 16.04 | 14.31 --------+--------+---------------+--------+----------------

[87] Kühne und Chittenden: Zeitschr. f. Biol., Band 19, pp. 167 and 178.

In both cases there is a noticeable decrease in nitrogen, and a corresponding increase in the content of carbon. Evidently, then, this cleavage of the albumin-molecule into the anti-group on the one hand, and into bodies of the hemi-group on the other, is accompanied by chemical changes of such magnitude that their imprint is plainly visible upon the resultant products; changes which certainly are far removed from those common to polymerization.

This proneness of proteid matter to undergo hydration and subsequent cleavage is further testified to by the readiness with which even such a resistant body as coagulated egg-albumin breaks down under the simple influence of superheated water at 130° to 150° C. Many observations are recorded bearing on this tendency of proteid matter, but few observers have carried their experiments to a satisfactory conclusion. A recent study of this question in my own laboratory, has given some very interesting results.[88] Thus, coagulated egg-albumin placed in sealed tubes with a little distilled water and exposed to a temperature of 150° C. for three to four hours, rapidly dissolves, leaving, however, an appreciable residue. The solution reacts alkaline, there is a separation of sulphur, and in the fluid is to be found not albumin, but two distinct albumose-like bodies, together with some true peptone, and a small amount of leucin, tyrosin, and presumably other bodies.[89] The albumose-like bodies are in many ways quite peculiar. In some respects they resemble the albumoses formed in ordinary digestion; but in others they show peculiarities which render them quite unique, so that they merit the specific name of atmidalbumoses, as suggested by Neumeister. What, however, I wish to call attention to here is the composition of these albumoses. Prepared from coagulated egg-albumin by the simple action of heat and water, they show a deviation from the composition of the mother-proteid, which plainly implies changes of no slight degree. This is clearly apparent from the following table:

================================================================== |Coagulated|Atmidalbumose| Atmidalbumose |Deutero- | | egg- | precipitated|precipitated by| atmid- |Antialbumid. | albumin. | by NaCl. | NaCl + acid. |albumose.| --+----------+-------------+---------------+---------+------------ C | 52.33 | 55.13 | 55.04 | 51.99 | 53.79 H | 6.98 | 6.93 | 6.89 | 6.60 | 7.08 N | 15.84 | 14.28 | 14.17 | 13.25 | 14.55 S | 1.81 | 1.66 | --- | 0.98 | --- O | 23.04 | 22.00 | --- | 27.18 | --- --+----------+-------------+---------------+---------+------------

[88] Chittenden and Meara: A Study of the Primary Products Resulting from the Action of Superheated Water on Coagulated Egg-albumin. Journal of Physiology, vol. 15, p. 501.

[89] Compare Neumeister’s experiments on blood-fibrin. Ueber die nächste Einwirkung gespannte Wasserdämpfe auf Proteine und über eine Gruppe eigenthümlicher Eiweisskörper und Albumosen. Zeitschr. f. Biol., Band 26, p. 57.

Here we see that two of these primary albumoses formed by the action of superheated water, like the previously described antialbumid, show a loss of nitrogen with a marked increase in the content of carbon. Evidently, they are related to the antialbumid formed by the action of dilute acid. They are, however, soluble in water, and in many ways differ from true antialbumid, but there is evidently an inner relationship. The so-called deuteroatmidalbumose shows a still more noticeable falling off in nitrogen and sulphur, while the content of carbon is more closely allied to that of the mother-proteid. The albumose precipitable by sodium chloride, although different from an albumid, evidently comes from the anti-group and is a cleavage product which in turn may undergo further hydration and splitting by continued treatment. The so-called deutero-body, on the other hand, may well be a representative of the hemi-group.[90]

[90] Compare Krukenberg, Sitzungsberichte der Jenaischen Gesellschaft für Medicin, etc. 1886.

It is not my purpose here to enter into details connected with the action of superheated water on proteids. Such a course would take us too far from our present subject, but I do wish to emphasize the fact that even the most resistant of proteids has an innate tendency to undergo hydration and cleavage, and that even simple heating with water alone, at a temperature slightly above 100° C., is sufficient to induce at least partial solution of the proteid. Further, this solvent action in the case of water and dilute acids, at least, is certainly associated with marked chemical changes. It is not mere solution, it is not simply the formation of one soluble body, but solution of the proteid is accompanied by the appearance of a row of new products, in which the terminal bodies are crystalline substances of simple composition. Further, this conclusion does not rest upon the results obtained from a single proteid, for I have at various times studied also the primary products formed in the cleavage of casein, elastin, zein, and other proteids by the action of hot dilute acid, and in all cases have obtained evidence of the formation of several proteose-like bodies, as well as of true peptones.

By the action of more powerful hydrolytic agents, such as boiling hydrochloric acid to which a little stannous chloride has been added to prevent oxidation, the proteid molecule may be completely broken down into simple decomposition products, of which leucin, tyrosin, aspartic acid, glutamic acid, glucoprotein, lysin, and lysatinin are typical examples.[91] In other words, by this and other methods of treatment, which we cannot take time to consider, we can easily break down the albumin-molecule completely into bodies which, as we shall see later on, are typical end-products of trypsin-proteolysis, and which are far removed from the original proteid. But, as we have seen, even the primary bodies formed in the less profound hydrolysis induced by superheated water, do not show the composition of the mother-proteid. Hydration and cleavage leave their marks upon the products, and thereby we know that solution of the proteid is the result of something more than a mere rearrangement of the atoms in the molecule.

[91] Hlasiwetz und Habermann, Ann. Chem. u. Pharm., Band 169, p. 150. Also Drechsel, Du Bois-Reymond’s Archiv f. Physiol., 1891, p. 255.