Abstract
IN a study of the action of pepsin on various poly-α-amino-acids we have found that poly-L-glutamic acid as well as some ammo-acid copolymers containing L-glutamic acid residues are readily hydrolysed by pepsin. Digestion was tested at 35° in 3 ml. solutions containing 12 mg of polyamino-acid1 and 0.8 mg crystalline pepsin, adjusted to pH. 2.3. Since most of the polypeptides investigated do not dissolve directly at acid pH, they were dissolved in the minimal amount of 0.1 N sodium hydroxide, and the required pH was obtained by adding 0.1 N hydrochloric acid. Hydrolysis was followed by measuring: (a) the uptake of acid in the pH-stat ; (b) the increase in the colour produced with ninhydrin2; (c) the increase in Van-Slyke amino-nitrogen. Fair agreement was found in the results obtained by the foregoing three methods. The peptic digests were analysed by descending paper chromatography in n-propanol/water/concentrated aqueous ammonia (100 : 50 : 1 v/v). The chromato-grams were run for 48 h, and were revealed with ninhydrin.
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NEUMANN, H., SHARON, N. & KATCHALSKI, E. Poly-α-amino-acids containing L-Glutamyl Residues as Substrates for Pepsin . Nature 195, 1002 (1962). https://doi.org/10.1038/1951002a0
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DOI: https://doi.org/10.1038/1951002a0
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