PT - JOURNAL ARTICLE AU - ROLAND D. CIARANELLO TI - Regulation of Phenylethanolamine <em>N</em>-Methyltransferase Synthesis and Degradation DP - 1978 May 01 TA - Molecular Pharmacology PG - 478--489 VI - 14 IP - 3 4099 - http://molpharm.aspetjournals.org/content/14/3/478.short 4100 - http://molpharm.aspetjournals.org/content/14/3/478.full SO - Mol Pharmacol1978 May 01; 14 AB - The steady-state levels of rat adrenal phenylethanolamine N-methyltransferase are under the control of adrenal glucocorticoids. Following hypophysectomy, enzyme levels fall dramatically; they can be restored to normal by the administration of adrenocorticotrophin or dexamethasone. The decline in enzyme levels after hypophysectomy is accompanied by a decrease in the number of immunotitratable enzyme molecules; dexamethasone treatment restores the immunochemically reactive transferase. The decrease in number of enzyme molecules after hypophysectomy is due to accelerated proteolysis; this is reversed by glucocorticoid administration. Phenylethanolamine N-methyltransferase from hypophysectomized rats is more vulnerable to proteolysis in vivo and to denaturation at 50° in vitro, suggesting that hypophysectomy causes fundamental changes in the overall stability of the enzyme.