Mitranic M M, Sturgess J M, Moscarello M A
Can J Biochem. 1979 Jul;57(7):1008-13. doi: 10.1139/o79-125.
The sialyltransferase and galactosyltransferase activities of the Golgi-rich fraction from rat liver were enhanced by the binding of wheat germ agglutinin (WGA). The sialytransferase was more sensitive than the galactosyltransferase to the WGA. Maximal stimulation of the galactosyltransferase activity resulted from the binding of 60--80 micrograms WGA to the Golgi membrane, while only 40 micrograms of WGA produced a maximal enhancement in the sialyltransferase activity. Within 5 min of WGA binding, the Golgi sialytransferase activity was doubled. After the initial binding of WGA to the Golgi fraction, the galactosyltransferase activity was decreased by 30%. However, in 15 min the activity was doubled by the binding of WGA. The activities of both enzymes were further enhanced by incubation for up to 90 min. The stimulation of both sialyltransferase and galactosyltransferase activities by WGA was reversed by N-acetyl-D-glucosamine (GlcNAc), the specific inhibitor of agglutination by WGA. Complete reversal of the enhanced activity was observed after 20--30 min in the presence of 1 micromol GlcNAc. The association constant for the binding of WGA to the Golgi membranes was calculated to be 4.16 X 10(-6) M from a Steck-Wallach plot. The 'n' value or mean binding sites was calculated as 5.26 X 10(-5) M/mg of Golgi membrane protein.
小麦胚凝集素（WGA）的结合增强了大鼠肝脏富含高尔基体部分的唾液酸转移酶和半乳糖基转移酶活性。唾液酸转移酶比半乳糖基转移酶对WGA更敏感。60 - 80微克WGA与高尔基体膜结合可使半乳糖基转移酶活性得到最大刺激，而仅40微克WGA就能使唾液酸转移酶活性得到最大增强。WGA结合后5分钟内，高尔基体唾液酸转移酶活性增加一倍。WGA最初与高尔基体部分结合后，半乳糖基转移酶活性降低了30%。然而，15分钟后，WGA的结合使该活性增加了一倍。两种酶的活性在长达90分钟的孵育后进一步增强。WGA对唾液酸转移酶和半乳糖基转移酶活性的刺激作用可被WGA凝集特异性抑制剂N - 乙酰 - D - 葡萄糖胺（GlcNAc）逆转。在1微摩尔GlcNAc存在的情况下，20 - 30分钟后观察到增强的活性完全逆转。根据Steck - Wallach图计算，WGA与高尔基体膜结合的缔合常数为4.16×10⁻⁶ M。“n”值或平均结合位点计算为5.26×10⁻⁵ M/毫克高尔基体膜蛋白
