Sucrose synthase of soybean nodules.
Sucrose synthase of soybean nodules.
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DOI：
10.1104/pp.78.1.149
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发表时间：
1985-05
期刊：
影响因子：
7.4
通讯作者：
M. Morell;L. Copeland
中科院分区：
文献类型：
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作者：
M. Morell;L. Copeland
蔗糖合成酶（UDPGLUCOSE：d-果糖2-α-d-葡糖基转移酶，EC 2.4.1.13）已从大豆（Glycine max L.）Merr cv威廉姆斯）结节。天然酶的分子量为40万。亚基分子量为90，000，并提出大豆根瘤蔗糖合成酶的四聚体结构。该酶在蔗糖裂解和合成方向的最佳活性分别为pH 6和pH9.5，并表现出典型的Michaelis-Menten动力学。大豆根瘤蔗糖合成酶对UDP具有高亲和力（K（m），5微摩尔），对ADP（表观K（m），0.13毫摩尔）和CDP（表观K（m），1.1毫摩尔）具有相对低的亲和力。蔗糖的K（m）为31毫摩尔。在合成方向上，UDP葡萄糖（K（m），0.012毫摩尔）是比ADP葡萄糖（K（m），1.6毫摩尔）更有效的葡萄糖基供体，果糖的K（m）为3.7毫摩尔。二价阳离子在切割和合成方向上都刺激活性，并且酶对重金属的抑制非常敏感。
SUCROSE SYNTHASE (UDPGLUCOSE: d-fructose 2-alpha-d-glucosyl transferase, EC 2.4.1.13) has been purified from the plant cytosolic fraction of soybean (Glycine max L. Merr cv Williams) nodules. The native enzyme had a molecular weight of 400,000. The subunit molecular weight was 90,000 and a tetrameric structure is proposed for soybean nodule sucrose synthase. Optimum activity in the sucrose cleavage and synthesis directions was at pH 6 and pH 9.5 respectively, and the enzyme displayed typical Michaelis-Menten kinetics. Soybean nodule sucrose synthase had a high affinity for UDP (K(m), 5 micromolar) and a relatively low affinity for ADP (apparent K(m), 0.13 millimolar) and CDP (apparent K(m), 1.1 millimolar). The K(m) for sucrose was 31 millimolar. In the synthesis direction, UDPglucose (K(m), 0.012 millimolar) was a more effective glucosyl donor than ADPglucose (K(m), 1.6 millimolar) and the K(m) for fructose was 3.7 millimolar. Divalent cations stimulated activity in both the cleavage and synthesis directions and the enzyme was very sensitive to inhibition by heavy metals.