MULTIPLE FORMS OF DOPAMINE BETA HYDROXYLASE

多巴胺β-羟化酶（DBH）是一种儿茶酚胺生物合成酶 存在于肾上腺髓质的嗜铬分泌泡内， 交感神经末梢和脑的去甲肾上腺素能神经元。 血清 还含有DBH活性。 在分泌囊泡中发现DBH， 两种形式，可溶性的和膜结合的。 膜的机理 附着和调节两种形式的胸径的比例不是 明白 对纯化的膜状胸径的分析表明， 磷脂酰丝氨酸特异性和紧密结合， 该形式的四分之一具有未切割的信号序列。 这两 特性可能影响膜附着。 在拟议的工作中，我们将测试的假设，磷脂酰丝氨酸， 调节多巴胺β-羟化酶的膜性与可溶性比率。 我们认为，成熟的加工DBH在果蝇中的表达 黑腹果蝇Schneider II细胞会导致一些酶成为 由于与磷脂酰胆碱的非共价相互作用而与膜结合。 此外，我们建议，这种相互作用可以直接测试， 耗尽施耐德细胞的磷脂酰丝氨酸 所提出的工作的结果将增加我们的知识膜 脂质-蛋白质相互作用，特别是对于不断增长的蛋白质类， 其通过与磷脂酰丝氨酸的相互作用结合到生物膜上。 此外，我们不知道是什么调节血清DBH的水平。 这种酶的可溶性与膜性形式的比例可能起着重要的作用。 在这个临床感兴趣的参数中起重要作用。

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.