Studies on UDPG-glycogen transglucosylase. I. Preparation and differentiation of two activities of UDPG-glycogen transglucosylase from rat skeletal muscle.
Studies on UDPG-glycogen transglucosylase. I. Preparation and differentiation of two activities of UDPG-glycogen transglucosylase from rat skeletal muscle.
复制标题
UDPG-糖原转葡萄糖基酶的研究。
DOI：
10.1021/bi00911a005
复制
发表时间：
1962
期刊：
影响因子：
2.9
通讯作者：
J. Larner,
中科院分区：
文献类型：
--
作者：
M. Rosell;C. Villar;J. Larner,
从大鼠肌肉中制备了两种活性明显不同的UPG-糖原转葡萄糖基酶。一个活动不需要葡萄糖-6-P，虽然刺激可以检测到在低浓度的UDPG。这种活性可以通过在30 ℃下在0.05M巯基乙醇中温育粗冻干酶制剂60至75分钟来制备。另一种活性依赖于葡萄糖-6-P的存在，可以通过在冷冻状态下老化肌肉并通过获得与100，000 X g颗粒级分相关的酶来制备。这两种活动进行了区分的葡萄糖-6-P和Mg++的存在下，UDPG依赖的动力学测量。给出了不同条件下的表观K_n。Mg ~（++）强烈地刺激葡萄糖-6-P非依赖性活性，降低表观K_n，而不改变V。葡萄糖-6-P、Mg ~（++）或两者一起具有相同的作用。Mg~（2+）对葡萄糖-6-P依赖性活性无明显刺激作用，但葡萄糖-6-P存在时，Mg~（2+）对葡萄糖-6-P依赖性活性无明显刺激作用。葡萄糖-6-P的刺激是由于V大大增加，也许是由于K略有降低。Villar-Palasi和Lamer（1960 a，B，1961）证明，当在无葡萄糖-6-P存在下测量时，从与胰岛素孵育的大鼠半横膈制备的提取物显示出增加的UDPG-糖原转葡糖基酶1活性。对照组和胰岛素处理组膈肌提取物的活性均增加，但无差异。在培养基中不存在葡萄糖的情况下，在隔膜与胰岛素孵育后也观察到无葡萄糖-6-P的酶活性增加。Steiner et al.（1961）报道了在注射胰岛素后2至4小时，四氧嘧啶糖尿病大鼠肝脏中的转葡糖基酶活性显著增加。用胰岛素预处理后，组织提取物中的差异表明，在肌肉中，酶活性增加，对葡萄糖-6-P的敏感性降低。对葡萄糖-6-
Two distinctly different activities of UDPG-glycogen transglucosylase were prepared from rat muscle in crude form. One activity did not require glucose-6-P, although stimulation could be detected at low concentrations of UDPG. This activity could be prepared by incubating a crude lyophilized enzyme preparation for 60 to 75 minutes at 30 in 0.05 M mercaptoethanol. The other activity, which was dependent on the presence of glucose-6-P, could be prepared by aging the muscle in the frozen state and by obtaining the enzyme associated with the 100,000 X g particulate fraction. Both activities were differentiated by kinetic measurements of the UDPG dependence in the presence of glucose-6-P and Mg++. The apparent K „under the varying conditions is given. Mg++ strongly stimulated the glucose-6-P independent activity, lowering the apparent K „with no alteration in V. Glucose-6-P, Mg++, or both togetherhad the same action. The glucose-6-P dependent activity was not stimulated by Mg~~ unless glucose-6-P was present. The stimulation due to glucose-6-P resulted fromgreatly increasing the V and, perhaps, from slightly decreasing the K „.Villar-Palasi and Lamer (1960a, b, 1961) dem-onstrated that extracts prepared from rat hemidiaphragms incubated with insulin exhibited in-creased UDPG-glycogen transglucosylase1 ac-tivity when measured in the absence of glucose-6-P. When measured in the presence of glucose-6-P, activities of extracts ofcontrol and insulintreated diaphragms were both increased and did not differ. This increase in enzyme activity without glucose-6-P was also observed after diaphragms were incubated with insulin in the absence of glucose in the medium. Steiner et al.(1961) reported a marked in-crease in transglucosylase activity in the livers of alloxan diabetic rats 2 to 4 hours after the injection of insulin. The differences noted in tissue extracts after pretreatment with insulin demon-strated an increased enzyme activity and a decreased sensitivity to glucose-6-P in the case of muscle. Differences in sensitivity to glucose-6-