Polyphosphoinositide biosynthesis in three subfractions of rat brain myelin
Polyphosphoinositide biosynthesis in three subfractions of rat brain myelin
复制标题
大鼠脑髓磷脂三个亚组分中多磷酸肌醇的生物合成
DOI：
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发表时间：
1978
影响因子：
4.7
通讯作者：
H. Brockerhoff
中科院分区：
文献类型：
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作者：
D. S. Deshmukh;W. D. Bear;H. Brockerhoff
脑内的多磷酸肌醇磷脂，即磷脂酰肌醇 - 4 - 磷酸（二磷酸肌醇，DPI）和磷脂酰肌醇 - 4,5 - 二磷酸（三磷酸肌醇，TPI），主要与髓鞘部分相关联，脑内大部分此类脂质存在于髓鞘中（艾希伯格和道森，1965年；豪泽和艾希伯格，1973年；谢赫和帕尔默，1976年）。DPI和TPI是通过单磷酸肌醇（PI）的逐步磷酸化合成的，单酯化磷酸的周转率是已知的所有脂质部分中最快的。PI激酶（ATP：磷脂酰肌醇 - 4 - 磷酸转移酶，EC 2.7.1.67）通常与质膜相关联（凯等人，1966年；哈伊伍德和霍索恩，1969年）；DPI激酶（ATP：磷脂酰肌醇 - 4 - 磷酸 - 5 - 磷酸转移酶，EC 2.7.1.68）在许多组织中是膜结合的（加勒特和雷德曼，1975年；图等人，1970年），但在脑上清液部分也有发现（凯等人，1968年）。这两种活性在脑微粒体和神经末梢（中岛和小西，1974年；沙赫特，1976年）以及髓鞘制剂中都能找到（艾希伯格和道森，1965年；沙赫特，1976年；亚科贝利，1969年）。膜层的紧密排列使得髓鞘结构的核心在代谢上相当难以接近；髓鞘中脂质和蛋白质周转缓慢就证明了这一点。因此，有人提出，高反应性的多磷酸肌醇磷脂及其激酶可能位于髓鞘附属结构中，如内、外轴系膜或郎飞结处的膜环，即在那些与神经胶质细胞质、轴膜或细胞外空间相邻的松散排列的髓鞘区域（艾希伯格和道森，1965年；豪泽和艾希 -
THE polyphosphoinositides, phosphatidylinositol-4-phosphate (diphosphoinositide, DPI) and phosphatidylinositol4,s-diphosphate (triphosphoinositide, TPI) of brain, are predominantly associated with the myelin fraction, which contains the bulk of these lipids present in brain (EICHBERG & DAWSON, 1965; HAUSER & EICHBERG, 1973; SHAIKH & PALMER, 1976). DPI and TPI are synthesized by stepwise phosphorylation of monophosphoinositide (PI), and the turnover rates of the monoesterified phosphates are the fastest such rates known for any lipid moiety. PI kinase (ATP:phosphatidylinositol-4-phosphotransferase, EC 2.7.1.67) is generally associated with plasma membranes (KAI et al., 1966; HAJ~WCOD & HAWTHORNE, 1969); DPI kinase (ATP: phosphatidylinositol-Cphosphate5-phosphotransferase. EC 2.7.1.68) is membrane bound in a number of tissues (GARRETT & REDMAN, 1975; TOU et al.. 1970) but is also found in a brain supernatant fraction (KAI et al.. 1968). Both activities are found in brain micros o m a and nerve endings (NAKAMUhA & KONISHI, 1974; SCHACHT, 1976) and in myelin preparations (EICHBERG & DAWSON, 1965; SCHACHT, 1976; IACOBELLI, 1969). The tight packing of membrane layers makes the core of the myelin structure rather inaccessible metabolically; this is attested by the sluggishness of lipid and protein turnover in myelin. It has, therefore, been suggested that the highly reactive polyphosphoinositides. and the kinases. might be located in myelin appurtenances such as the internal or external mesaxon or the membrane loops at the nodes of Ranvier, i.e. in those loosely packed myelin regions adjacent to glial cytoplasm, axolemma. or extracellular space (EICHBERG & DAWSON, 1965; HAUSER & EICH-