Researches on the nature of enzyme-action. I, On the causes of the rise in electrical conductivity under the action of trypsin / by W.M. Bayliss.

  • William Bayliss
Date:
[1907?]
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Licence: Public Domain Mark

Credit: Researches on the nature of enzyme-action. I, On the causes of the rise in electrical conductivity under the action of trypsin / by W.M. Bayliss. Source: Wellcome Collection.

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    Aspartic acid then, contrary to the mono-carboxylic acids, has a high conductivity. This is in agreement with its other properties as a fairly strong acid’. In fact when we consider that one carboxyl group is more than sufficient to neutralize the effect of the NH, we see that the second COOH is more or less free to exert its H+ ion-producing power. Glutamic acid. This body is of much importance in the hydrolytic action of trypsin, since it is contained in considerable proportion in most proteins*, I have had some difficulty in preparing it in a state of sufficient purity for conductivity determinations, but found the best method to be from the hydrochloride which separates out from the products of hydrolysis of casein on saturation with HCl’. This was recrystal- lized and then decomposed by moist silver oxide. To free the solution from ammonia it was evaporated in vacuo at 40° and the silver glutamate decomposed in the usual way by sulphuretted hydrogen. The free acid was then recrystallized five times from conductivity water. It was soluble to the extent of 1:76 °/, in water at 38°5°. Its melting-point was 195° by the method of Kutscher and Otori. In my hands, however, this method gives results about 5° lower than the ordinary method of immersion in sulphuric acid. Its specific rotatory power was [a], = +29°6° when dissolved in equivalent amount of HCl. This value is very slightly below that found by Fischer; my preparation was probably racemized to a small extent by the silver oxide used. The conductivity of a 1°76 °/, solution was, at 39°4°, 857 gemmhos. From this value that of a 5 solution (1°471°/)) would be 716 gemmhos, A second determination was made on a specimen kindly placed at my disposal by Dr Aders Plimmer. This was obtained from hydrolysis of gelatin. It had a melting-point of 205° and was soluble in water to the extent of 1:975°/) at 39°. The conductivity of this solution was 1104 gemmhos or for i 822 gemmhos. It was therefore not quite so pure as the first preparation, but had only been once recrystallized. A third preparation was made from the di-ethyl-ester. The recrystallized glutamic acid hydrochloride was esterified by HCl gas in the usual way*. The ester, set free by potas- sium carbonate, distilled over at 15 mm. Hg and temperature of oil-bath of 115°—120° C. It was hydrolyzed after removal of the phenyl-alanine ester by ether®, by heating on the water-bath with a known amount of barium hydroxide, which was afterwards removed 1 See Walden, Zeitsch. f. physik. Chem. vi. p. 482. 1891. 2 See the table in Cohn heim’s Chemie d, Eiweisskérper, 2° Aufl. 1904, pp. 42—47, 3 For two samples of this substance my thanks are due to Mr P. Hamill of the Cambridge Physiological Laboratory. In the filtration of small amounts of the hydrochloride from strong hydrochloric acid the platinum-sieve filter will be found of much service. (Aders Plimmer and Bayliss, This Journal, xxx1. p. 439. 1906.) 4 Fischer, Ber. d. D. chem. Gesellsch, xxxtv. p. 433. 1901. 5 Fischer, Unters. iiber Amino-siiuren, Polypeptiden u.s.w. S. 59. 1906.
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