大鼠睾丸颗粒性及去污剂增溶的腺苷酸环化酶的特性。促卵泡激素刺激的作用。

Properties of particulate and detergent-solubilized adenylate cyclase of rat testis. Effects of follitropin stimulation.

作者信息

Abou-Issa H, Reichert L E

出版信息

Biochim Biophys Acta. 1978 Oct 12;526(2):613-25. doi: 10.1016/0005-2744(78)90152-3.

Abstract

Basal, fluoride and follitropin stimulated activities of adenylate cyclase have been studied in the testes of immature rats. The enzyme was maximally activated (about twice the basal activity) by low concentrations of follitropin, with an apparent Km of about 9 . 10(-10) M. Both Mg2+ and Mn2+ activate the enzyme but the apparent Ka for Mg2+ is about 10 times that for Mn2+. However, the apparent Km values for MgATP2- and MnATP2- are nearly the same (1.4 . 10(-4) M) and the cation activation of the enzyme is mainly through an increase in V. Ca2+ inhibited all expressions of testicular adenylate cyclase activity. Follitropin and fluoride stimulated adenylate cyclase activity at all Mg2+ concentrations but did not significantly affect the apparent Ka for Mg2+ or the Km for the substrate (MgATP2-). The stimulatory effect of the hormone or fluoride is mainly through an increase in V. Testicular adenylate cyclase could be solubilized with Triton X-100 or Lubrol-PX. The detergent-solubilized enzyme exhibited Km for substrate and Ka values for divalent cations similar to those of the membrane-bound enzyme and remained responsive to stimulation by fluoride. The stimulatory effect of follitropin, however, was lost. Responsiveness to follitropin was also lost by membrane-bound adenylate cyclase after treatment with phospholipase, although the fluoride effect was unchanged. These results reflect the essential role of lipids in the regulation of the follitropin-specific response.

摘要

已对未成熟大鼠睾丸中基础状态、氟化物及促卵泡激素刺激下的腺苷酸环化酶活性进行了研究。低浓度促卵泡激素可使该酶活性最大程度激活（约为基础活性的两倍），其表观 Km 约为 9×10⁻¹⁰ M。Mg²⁺和 Mn²⁺均可激活该酶，但 Mg²⁺的表观 Ka 约为 Mn²⁺的 10 倍。然而，MgATP²⁻和 MnATP²⁻的表观 Km 值几乎相同（1.4×10⁻⁴ M），且阳离子对该酶的激活主要是通过增加 Vmax 实现的。Ca²⁺抑制睾丸腺苷酸环化酶活性的所有表现形式。在所有 Mg²⁺浓度下，促卵泡激素和氟化物均刺激腺苷酸环化酶活性，但对 Mg²⁺的表观 Ka 或底物（MgATP²⁻）的 Km 无显著影响。激素或氟化物的刺激作用主要是通过增加 Vmax 实现的。睾丸腺苷酸环化酶可用 Triton X - 100 或 Lubrol - PX 进行增溶。去污剂增溶的酶对底物的 Km 和对二价阳离子的 Ka 值与膜结合酶相似，且仍对氟化物刺激有反应。然而，促卵泡激素的刺激作用丧失。用磷脂酶处理后，膜结合腺苷酸环化酶对促卵泡激素的反应性也丧失，尽管氟化物的作用未改变。这些结果反映了脂质在促卵泡激素特异性反应调节中的重要作用。