Abstract
PREVIOUS work in this laboratory showed that the activity of the overall oxidation of tyrosine by rat liver systems was reduced after administration of thyroid preparations to normal rats, to hypophysectomized rats or to thyroparathyroidectomized rats, with respect to their appropriate controls1. At the same time, investigations were extended in vitro to show that the overall oxidations of tyrosine and of p-hydroxyphenylpyruvate were inhibited by thyroxine, and that tyrosine transaminase was more sensitive to the in vitro action of the hormone than was p-hydroxyphenylpyruvate oxidation. Further and more recent work with the tyrosine transaminase system in vitro2 has shown that thyroxine interacts with pyridoxal phosphate in a complicated fashion and that for this interaction to occur the presence of tyrosine is mandatory. This communication provides information which explains in large part the reduction of the overall tyrosine oxidation capacity of liver following administration of thyroid hormone in vivo.
Similar content being viewed by others
References
Litwack, G., J. Biol. Chem., 228, 823 (1957).
Diamondstone, T. I., and Litwack, G., Fed. Proc., 22, 2234 (1963); J. Biol. Chem. (in the press).
Al-Nejjar, Z. H., and Litwack, G., Biochim. Biophys. Acta, 48, 153 (1961).
Lin, E. C. C., and Knox, W. E., Biochim. Biophys. Acta, 26, 85 (1957).
Canellakis, A. N., and Cohen, P. P., J. Biol. Chem., 222, 53 (1956).
Briggs, A. P., J. Biol. Chem., 51, 453 (1922).
La Du, B. N., and Zannoni, V. G., J. Biol. Chem., 217, 777 (1955).
Bass, A. D., McArdle, A. H., and Grisham, J. W., Science, 128, 372 (1956).
Rivlin, R. S., and Levine, B. J., Endocrinol., 73, 103 (1963).
Knox, W. E., and Goswami, M. N. D., J. Biol. Chem., 235, 2662 (1960).
Zannoni, V. G., and La Du, B. N., J. Biol. Chem., 235, 2667 (1960).
Sokoloff, L., and Kaufman, S., J. Biol. Chem., 236, 795 (1961).
Tata, J. R., Nature, 197, 1167 (1963).
Litwack, G., Ebert, P. S., Yankelowitz, S., and Taylor, M. W., Enzymologia, 20, 183 (1959).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
LITWACK, G., AL-NEJJAR, Z., SEARS, M. et al. Time-course of Tyrosine Transaminase and p-Hydroxyphenylpyruvate Oxidase Activities during Thyroid Administration. Nature 201, 1028–1029 (1964). https://doi.org/10.1038/2011028a0
Issue Date:
DOI: https://doi.org/10.1038/2011028a0
- Springer Nature Limited