Tyrosine hydroxylase in human adrenal and pheochromocytoma: localization, kinetics, and catecholamine inhibition

J. C. Waymire; N. Weiner; F. H. Schneider; M. Goldstein; L. S. Freedman

doi:10.1172/JCI106981

^{Department of Pharmacology, University of Colorado School of Medicine, Denver, Colorado 80220}

^{Department of Psychiatry, New York University Medical Center, New York 10016}

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^{Department of Pharmacology, University of Colorado School of Medicine, Denver, Colorado 80220}

^{Department of Psychiatry, New York University Medical Center, New York 10016}

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^{Department of Pharmacology, University of Colorado School of Medicine, Denver, Colorado 80220}

^{Department of Psychiatry, New York University Medical Center, New York 10016}

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^{Department of Pharmacology, University of Colorado School of Medicine, Denver, Colorado 80220}

^{Department of Psychiatry, New York University Medical Center, New York 10016}

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^{Department of Pharmacology, University of Colorado School of Medicine, Denver, Colorado 80220}

^{Department of Psychiatry, New York University Medical Center, New York 10016}

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Published in Volume 51, Issue 7 on July 1, 1972
J Clin Invest. 1972;51(7):1798–1804. https://doi.org/10.1172/JCI106981.
© 1972 The American Society for Clinical Investigation

Published July 1, 1972 - Version history

The properties of partially purified tyrosine hydroxylase from six pheochromocytomas were compared with partially purified normal human and bovine adrenal medulla enzyme. Substrate and inhibition kinetics, cofactor requirements, and intracellular localization of the enzyme from normal and tumor chromaffin tissue of humans were similar, as was the amount of enzyme activity per gram of tissue. Contrary to previous reports, the sensitivity to catecholamine inhibition of the pheochromocytoma enzyme from the six tumors studied was similar to that of both human and bovine adrenal medulla tyrosine hydroxylase. These results suggest that the excessive synthesis and secretion of catecholamines in some pheochromocytomas is not the result of a reduced sensitivity of tyrosine hydroxylase to catecholamine inhibition.