牛腎上腺髓質中蛋白磷酸水解酶之部份純化及其特性研究   全文下載

Partial Purification and Characterization of Protein Phosphatases from Bovine Adrenal Medulla

調控神經傳導物質的分泌及合成是藉由二級信差改變細胞內重要酵素及蛋白之磷酸化狀態來達成。在神經細胞中對於調控蛋白磷酸化的蛋白激?所扮演的角色了解不多，對於調控蛋白去磷酸化的蛋白磷酸水解?所知更少。本文主要是藉由高效液相層析（HPLC）之分離、基質特異性、抑制劑之敏感性等特性來檢測牛腎上腺髓質中蛋白磷酸水解?之活性。藉由HPLC離子交換DEAE層析柱的分離，均質後之牛腎上腺髓質上清液最少發現有4支不同的蛋白磷酸水解?活性波峰（波峰I, II, III, IV）這些蛋白磷酸水解?對不同的基質呈現不同的特異活性。波峰IV對乳酪蛋白基質具有最高酵素活性，進一步分析發現該蛋白磷酸水解?對磷氧基?激?（phosphorylase kinase）基質之α次單位體較β次單位體具有較高之磷酸水解能力，並且該磷酸水解?可被okadaic acid強烈抑制，分子量的比對亦發現該波峰IV磷酸水解?與已知哺乳類細胞之異三位體2A型蛋白磷酸水解?相近，因此該磷酸水解?可能為2A型蛋白磷酸水解?。"

Control of neurosecretion and synthesis of neurotransmitters appears to be regulated through second messengers that change the phosphorylation state of critical enzymes and proteins. Relatively little is known about the role of protein kinases in these processes in neuronal cells and even less is known about the role of protein phosphatases. We have examined the phosphatase activities of the bovine adrenal medulla using chromatographic separation, substrate specificity and inhibitor sensitivity. When fractionated, using an HPLC ion exchange DEAE column, four distinct peaks (peaks I, II, III and IV) of phosphatase activity were observed in the supernatant of homogenized bovine adrenal medulla. These phosphatases have distinctly different specific activities toward different substrates. Peak IV which contains most of the activity toward phosphocasein, showed preferential dephosphorylation of theα subunit of phosphorylase kinase relative to the β subunit and was strongly inhibited by okadaic acid, attributes of the type 2A phosphatase. The apparent molecular weight of phosphatase peak IV is also comparable to the heterotrimeric form of the known protein phosphatase type 2A of mammalian cells.