猪胚胎肝脏微粒体中甘露糖基和N-乙酰葡糖胺-1-磷酸转移酶对磷酸多萜醇的特性

Properties of mannosyl- and N-acetylglucosamine-1-phosphate transferases towards dolichol phosphate in liver microsomes from pig embryos.

Zhivkov V I, Kyosseva S V, Panayotov B N, Kyossev Z N

Institute of General and Comparative Pathology, Bulgarian Academy of Sciences, Sofia.

Int J Biochem. 1988;20(1):67-71. doi: 10.1016/0020-711x(88)90012-2.

Abstract

The activity of mannosyl- and N-acetylglucosamine-1-phosphate transferases in microsomes from pig embryonic liver was linear to 1 min of incubation at 37 degrees C. 2. The activity of both enzymes was higher in the presence of Mg2+ as compared to Mn2+. A maximal stimulatory effect of Mn2+ was obtained at 2 mM concentration and greater concentrations of it inhibited the activities of both enzymes. 3. The activity of mannosyl transferase was found to be highest after treatment of microsomes with Nonidet P-40 while the activity of N-acetylglucosamine-1-phosphate transferase was greatest in the presence of sodium deoxycholate. 4. The Km for acceptor substrate was 1.6 x 10(-5)M in the reaction for dolichol phosphate mannose synthesis and 2.2 x 10(-5)M in the reaction for dolichol pyrophosphate N-acetylglucosamine formation. 5. The Km for GDP-mannose was 1.4 x 10(-5)M and for UDP-N-acetylglucosamine-6.2 x 10(-5)M. At saturating concentrations of donor substrates V values (pmol/min/mg) were 1330 and 150, respectively.

摘要

猪胚胎肝脏微粒体中甘露糖基转移酶和N-乙酰葡糖胺-1-磷酸转移酶的活性在37℃孵育1分钟时呈线性关系。2. 与Mn2+相比，Mg2+存在时两种酶的活性更高。Mn2+在2 mM浓度时获得最大刺激作用，更高浓度则抑制两种酶的活性。3. 发现用诺乃洗涤剂P-40处理微粒体后甘露糖基转移酶的活性最高，而在脱氧胆酸钠存在时N-乙酰葡糖胺-1-磷酸转移酶的活性最大。4. 在磷酸多萜醇甘露糖合成反应中，受体底物的Km为1.6×10(-5)M，在焦磷酸多萜醇N-乙酰葡糖胺形成反应中为2.2×10(-5)M。5. GDP-甘露糖的Km为1.4×10(-5)M，UDP-N-乙酰葡糖胺的Km为6.2×10(-5)M。在供体底物饱和浓度下，V值（pmol/分钟/毫克）分别为1330和150。