Abstract
SUMMARY 1. 1-Nitroso-2-naphthol reacts with both tyrosine and tyramine to form a red-colored product which gradually changes to a stable yellow chromo- phore. 2. The yellow compound obtained by treating tyramine with nitroso- naphthol has been isolated. Analysis indicates it to be the product of combination of 1 mole equivalent of each with the loss of 1 mole of water. 3. This reaction has been applied to the determination of tyrosine and tyramine in tissues and to the determination of tyrosine in protein hy- drolysates. 4. New determinations of the tyrosine content of bovine serum albumin and of lysozyme are reported. BIBLIOGRAPHY 1. Gerngross, O., Voss, K., and Herfelt, T., Ber. chem. Ges., 66, 435 (1933). 2. Thomas, L. E., Arch. Biochem., 6, 175 (1944). 3. Giral, J., An. inst. invest. cient. Univ. Nuevo Le6n, 1, 115 (1944). 4. Snell, F. D., and Snell, C. T., Calorimetric methods of analysis, New York, 200 (1937). 5. Block, R. J., and Bolling, D., The amino acid composition of proteins and foods, 2nd edition, Springfield, 114 (1951). 6. Folin, O., and Ciocalteu, V., J. Biol. Chem., 73, 627 (1927). 7. Bernhart, F. W., and Schneider, R. W., Am. J. Med. SC., 205, 636 (1943). 8. Stein, W. H., and Moore, S., Cold Spring Harbor Symposia Quant. Biol., 14, 179 (1949). 9. Shemin, D., J. Biol. Chem., 169, 439 (1945). 10. Velick, S. F., and Ronzoni, E., J. Biol. Chem., 173, 627 (1948). 11. Gunness, M., Dwyer, I. M., and Stokes, J. L., J. Biol. Chem., 163, 159 (1946). 12. Fromageot, C., Cold Spring Harbor
Highlights
The method does not distinguish between tyrosine and tyramine
It has been shown that tyramine and nitrosonaphthol react mole for mole, with loss of water, to form a stable yellow compound
At present the method is best suited to metabolic studies which involve the assay of tyrosine or tyramine in tissues to which the compounds or their precursors have been added in relatively large amount
Summary
To 1.0 ml. of plasma or tissue extract are added 3.0 ml. of water and 1.0 ml. of 30 per cent trichloroacetic acid and the mixture is centrifuged after 10 minutes. To 2 ml.[3] of the deproteinized plasma, tissue extract, or protein hydrolysate containing 0.03 to 0.80 PM of tyrosine or tyramine[4] in a glass-stoppered centrifuge tube, are added 1 ml. To an aliquot of the solvent is added an equal volume of n-heptane, and the tyramine is returned to an aqueous phase by shaking the solution with 0.2 N HCl. A portion of the acid extract is used for the reaction with nitrosonaphthol. When tyrosine is carried through the procedure, the resulting optical density is only about 57 per cent of the theoretical value, assuming that the molecular extinction coefficients of the nitrosonaphthol derivatives of tyrosine and tyramine are the same. About 27 per cent of the tyrosine undergoes nitration and about 19 per cent of the nitrosonaphthol derivative is removed by the ethylene dichloride extraction
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