Abstract
Rat adrenal tyrosine hydroxylase appears to exist in two forms that differ primarily in their affinities for pterin cofactor. In the nonstressed rat that has been anesthetized either by halothane or pentobarbital, approximately 25% of adrenal tyrosine hydroxylase is in the activated (low Km) form. Following decapitation, approximately 60% of the enzyme is found in the active (low Km) form, suggesting that a considerable fraction of the less active form of the enzyme is rapidly transformed to the active form during stress. A similar, although more complete, transformation of the less active form of the enzyme to the active form can be produced if the soluble enzyme from either stressed or nonstressed rats is incubated in the presence of cyclic AMP-dependent protein phosphorylating system. In the presence of the cyclic AMP-dependent protein phosphorylating system, the enzyme from both stressed and nonstressed animals achieves a comparable degree of activation. These results suggest that stress related activation of tyrosine hydroxylase may be mediated by a cyclic AMP-dependent protein kinase reaction.
- Copyright © 1979 by Academic Press, Inc.
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