Hirata M, Yanaga F, Koga T, Ogasawara T, Watanabe Y, Ozaki S
Department of Biochemistry, Faculty of Dentistry, Kyushu University, Fukuoka, Japan.
J Biol Chem. 1990 May 25;265(15):8404-7.
A series of DL-inositol 1,4,5-trisphosphate (IP3) analogs, with a bulky substitutent on the 2nd carbon of the inositol ring, has been synthesized. These compounds exert biological activities with only minor reduction in potency, in several assay systems (Hirata, M., Watanabe, Y., Ishimatsu, T., Ikebe, T., Kimura, Y., Yamaguchi, K., Ozaki, S., and Koga, T. (1989) J. Biol. Chem. 264, 20303-20308). Two analogs with aminocyclohexanecarbonyl (designated as analog 206) or aminobenzoyl group (analog 209) were separated into individual optical isomers and examined for stereospecificity in recognition by IP3-5-phosphatase, IP3-3-kinase and IP3 binding activity. IP3-5-phosphatase activity of erythrocyte ghosts was competitively inhibited by L-209 with a lower Ki value than D-IP3, but with a higher Ki value by L-206. D-Isomers of both analogs at 100 microM failed to inhibit the hydrolysis of D-[3H]IP3. On the other hand, D-isomers but not L-isomers of both analogs were as potent as D-IP3 in the recognition by IP3-3-kinase of rat brain cytosol and only the D-isomer of analog 206 could serve as substrate for the kinase. Also D-isomers of both analogs were equipotent to D-IP3 in displacing [3H]IP3 binding to rat cerebellum microsomes. These observations suggest that the IP3 analogs we synthesized are stereospecifically recognized by three IP3-recognizable proteins, but the phosphatase recognizes opposite isomers. Such being the case, the second hydroxyl group of D-IP3 may be involved in the recognition by IP3-5-phosphatase, but not by IP3-3-kinase and binding sites.
已经合成了一系列在肌醇环的第二个碳原子上带有庞大取代基的DL-肌醇1,4,5-三磷酸（IP3）类似物。在几种检测系统中，这些化合物发挥生物活性时效力仅有轻微降低（平田，M.，渡边，Y.，石松，T.，池部，T.，木村，Y.，山口，K.，尾崎，S.，和古贺，T.（1989）《生物化学杂志》264，20303 - 20308）。将带有氨基环己烷羰基（命名为类似物206）或氨基苯甲酰基（类似物209）的两种类似物拆分为各自的旋光异构体，并检测它们在被IP3 - 5 - 磷酸酶、IP3 - 3 - 激酶识别以及IP3结合活性方面的立体特异性。红细胞膜的IP3 - 5 - 磷酸酶活性被L - 209竞争性抑制，其Ki值低于D - IP3，但被L - 206抑制时Ki值更高。两种类似物的D - 异构体在100 microM时未能抑制D - [3H]IP3的水解。另一方面，两种类似物的D - 异构体而非L - 异构体在大鼠脑细胞质的IP3 - 3 - 激酶识别方面与D - IP3效力相当，并且只有类似物206的D - 异构体可作为该激酶的底物。两种类似物的D - 异构体在取代与大鼠小脑微粒体结合的[3H]IP3方面也与D - IP3效力相当。这些观察结果表明，我们合成的IP3类似物被三种可识别IP3的蛋白质立体特异性识别，但磷酸酶识别相反的异构体。既然如此，D - IP3的第二个羟基可能参与IP3 - 5 - 磷酸酶的识别，但不参与IP3 - 3 - 激酶和结合位点的识别。
