MULTIPLE FORMS OF DOPAMINE BETA HYDROXYLASE

多巴胺β-羟基酶是一种儿茶酚胺生物合成酶。 存在于肾上腺髓质嗜铬细胞分泌囊泡内， 交感神经末梢和大脑的去甲肾上腺素能神经元。血清 还包含胸径活动。在分泌囊中，DBH存在于 两种形式，可溶的和膜结合的。膜的作用机制 两种形式胸径比例的依附性和调节性不强 明白了。对提纯的膜胸径的分析表明，它具有 磷脂酰丝氨酸特异性和紧密结合，并且大约 这种形式的四分之一具有未切割的信号序列。这两个都是 特性可能会影响膜附着。 在拟议的工作中，我们将检验磷脂酰丝氨酸的假设 调节多巴胺β-羟基酶的膜与可溶性的比例。 我们认为成熟的加工胸径在果蝇中的表达 黑素胃酸施耐德II细胞将导致某些酶成为 由于与磷脂酰胆碱的非共价相互作用而形成的膜结合。 此外，我们建议可以通过以下方式直接测试这种交互作用 耗尽施耐德细胞的磷脂酰丝氨酸。 拟议工作的结果将增加我们对膜的了解 脂-蛋白相互作用，特别是对不断增长的一类蛋白质 它们通过与磷脂酰丝氨酸相互作用结合到生物膜上。 此外，我们不知道是什么调节了血清DBH的水平。 这种酶的可溶性形式与膜性形式的比率可能起到 在这一临床感兴趣的参数中有重要作用。

Dopamine beta-hydroxylase (DBH) is a catecholamine biosynthetic enzyme present inside chromaffin secretory vesicles of adrenal medulla, sympathetic nerve endings, and noradrenergic neurons of the brain. Serum also contains DBH activity. Within the secretory vesicles DBH is found in two forms, soluble and membrane-bound. The mechanism of membrane attachment and regulation of the ratio of the two forms of DBH is not understood. Analysis of purified membranous DBH has shown that it has phosphatidylserine specifically and tightly bound and that approximately one quarter of this form has uncleaved signal sequence. Both of these characteristics may influence membrane attachment. In the proposed work we will test the hypothesis that phosphatidylserine regulates the membranous to soluble ratio of dopamine beta-hydroxylase. We propose that the expression of the mature processed DBH in Drosophila melanogaster Schneider II cells will result in some of that enzyme becoming membrane-bound due to non-covalent interactions with phosphatidylerine. Further, we propose that this interaction can be directly tested by depleting the Schneider cells of phosphatidylserine. The results of the proposed work will increase our knowledge of membrane lipid-protein interactions, especially for the growing class of proteins which bind to biological membranes via interaction with phosphatidylserine. In addition, we do not understand what regulates the levels of serum DBH. The ratio of soluble to membranous forms of this enzyme may play a significant role in this parameter of clinical interest.