以二磷酸鸟苷 -D-葡萄糖和二磷酸鸟苷 -D-甘露糖为原料进行多糖生物合成的速率研究。

Rate studies of polysaccharide biosynthesis from guanosine diphosphate -D-glucose and guanosine diphosphate -D-mannose.

作者信息

Villemez C L

出版信息

Biochem J. 1971 Jan;121(1):151-7. doi: 10.1042/bj1210151.

DOI:10.1042/bj1210151

PMID:5000595

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC1176498/

Abstract

With enzyme preparations from Phaseolus aureus seedlings, the initial rate of (14)C-labelled polysaccharide formation from GDP-alpha-d-[(14)C]glucose is not increased by additions of GDP-alpha-d-mannose. However, final incorporation is increased by addition of GDP-alpha-d-mannose, since the total reaction-time is extended. In contrast, the initial rate of (14)C-labelled polysaccharide formation from GDP-alpha-d-[(14)C]mannose is increased by all concentrations of GDP-alpha-d-glucose that are less than that of the GDP-alpha-d-[(14)C]mannose. Maximum stimulation of the initial rate occurs at a GDP-alpha-d-[(14)C]mannose/GDP-alpha-d-glucose concentration ratio of about 4:1. However, eventual incorporation from GDP-alpha-d-[(14)C]mannose is decreased by the addition of GDP-alpha-d-glucose, since the reaction rate falls off sharply after about 2min. Reciprocal plots of (14)C-labelled polysaccharide formation from GDP-alpha-d-[(14)C]mannose result in biphasic graphs. The two straight-line portions of the plot are joined by a curved line in the concentration range between 2-3 and 50mum. Extrapolated K(m) values for the two linear components are 0.4-1.0 and 700-1500mum. The effect of GDP-alpha-d-glucose on the kinetics of (14)C-labelled polysaccharide formation from GDP-alpha-d-[(14)C]mannose is complex, and depends on relative concentrations of the two sugar nucleotides. (14)C-labelled polysaccharide formation from GDP-alpha-d-[(14)C]glucose also results in biphasic reciprocal plots. One component appears to have K(m) about 2-3mum, the other about 200-400mum. In this reaction, GDP-alpha-d-mannose appears to be a competitive inhibitor with K(i) 20-30mum. With particulate preparations of P. aureus, GDP-alpha-d-[(14)C]glucose appears to be a precursor for the synthesis of one polysaccharide, a glucomannan, the mannose moieties of which are derived from an intermediate existing in the particulate preparation. From the rate results, GDP-alpha-d-[(14)C]mannose appears to be a precursor for at least two polysaccharides, one of which is a glucomannan.

摘要

使用金甲豆幼苗的酶制剂时，添加GDP-α-D-甘露糖不会提高由GDP-α-D-[(14)C]葡萄糖形成(14)C标记多糖的初始速率。然而，由于总反应时间延长，添加GDP-α-D-甘露糖会增加最终掺入量。相比之下，所有浓度低于GDP-α-D-[(14)C]甘露糖的GDP-α-D-葡萄糖都会提高由GDP-α-D-[(14)C]甘露糖形成(14)C标记多糖的初始速率。初始速率的最大刺激发生在GDP-α-D-[(14)C]甘露糖/GDP-α-D-葡萄糖浓度比约为4:1时。然而，添加GDP-α-D-葡萄糖会降低最终由GDP-α-D-[(14)C]甘露糖的掺入量，因为反应速率在约2分钟后急剧下降。由GDP-α-D-[(14)C]甘露糖形成(14)C标记多糖的倒数作图得到双相图。该图的两条直线部分在2 - 3至50μm的浓度范围内由一条曲线连接。两个线性成分的外推K(m)值分别为0.4 - 1.0和700 - 1500μm。GDP-α-D-葡萄糖对由GDP-α-D-[(14)C]甘露糖形成(14)C标记多糖动力学的影响很复杂，并且取决于两种糖核苷酸的相对浓度。由GDP-α-D-[(14)C]葡萄糖形成(14)C标记多糖也会得到双相倒数作图。一个成分的K(m)约为2 - 3μm，另一个约为200 - 400μm。在该反应中，GDP-α-D-甘露糖似乎是一种竞争性抑制剂，K(i)为20 - 30μm。使用金甲豆的颗粒制剂时，GDP-α-D-[(14)C]葡萄糖似乎是一种葡甘露聚糖多糖合成的前体，其甘露糖部分来源于颗粒制剂中存在的一种中间体。从速率结果来看，GDP-α-D-[(14)C]甘露糖似乎是至少两种多糖的前体，其中一种是葡甘露聚糖。