Purification of Human Plasma Dopamine-B-Hydroxylase

摘要

Dopamine beta hydroxylase (DBH) catalyzes the biosynthesis of norepinephrine from dopamine in the biosynthetic pathway for catecholamines. The enzyme is localized within the synaptic vesicles of the sympathetic nerve terminals, the storage vesicles of adrenal medulla chromaffin cells, and peripheral and central sympathetic nerve terminals. The most frequently used source of the enzyme is the bovine adrenal medulla, but it has been isolated from sheep adrenals, rat adrenals, human pheochromocytoma, and human serum of plasma. The release of DBH accompanies the secretion of neurotransmitters by exocytosis from the vesicles of sympathetic nerve terminals and from the storage vesicles of sympathetic nerve terminals and from the storage vesicles of adrenal medulla chromaffin cells. Consequently, the enzyme has been considered a potential marker for the study of noradrenergic nerve and chromaffin cell function. Levels of the enzyme are elevated in patients with pheochromocytoma and decline after removal of the tumor. However, plasma levels vary widely among individuals. The variations may be related more to genetic factors than to sympathetic nerve activity. This report describes a purification procedure for human plasma DBH as a preliminary step in the development of an analytical tool for studying the various forms of the human enzyme in crude preparations, including plasma. This may serve as the basis for continuing studies on the levels of DBH in cold stress or acclimation and on ways to ameliorate the adverse effects of cold stress.