INHIBITION OF ADENYLOSUCCINATE SYNTHETASE + ADENYLOSUCCINATE LYASE FROM EHRLICH ASCITES-TUMOUR CELLS BY 6-THIOINOSINE 5]-PHOSPHATE
INHIBITION OF ADENYLOSUCCINATE SYNTHETASE + ADENYLOSUCCINATE LYASE FROM EHRLICH ASCITES-TUMOUR CELLS BY 6-THIOINOSINE 5]-PHOSPHATE
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DOI：
10.1042/bj0920398
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发表时间：
1964-01-01
影响因子：
4.1
通讯作者：
MORTON, RK
中科院分区：
文献类型：
--
作者：
ATKINSON, MR;MURRAY, AW;MORTON, RK
测定了埃利希腹水肿瘤细胞提取物中腺苷酸琥珀酸合成酶、腺苷酸琥珀酸裂解酶和肌苷-5-磷酸脱氢酶的表观活性，这些提取物在15度下保存了93天。在新鲜细胞的提取物中，合成酶的活性大于脱氢酶的活性，小于裂解酶的活性。从腹水肿瘤细胞腺苷琥珀酸合成酶的干扰活动，并用于腺苷琥珀酸合成的动力学研究。在pH7.5时，鸟苷5[image]-三磷酸的米氏常数（Km）为0.1 mM，L-天冬氨酸的Km为0.05 mM，肌苷5[image]-磷酸的Km为0.03 mM。6-硫代肌苷5[image]-磷酸是肌苷5[image]-磷酸转化为腺苷琥珀酸的非竞争性抑制剂;抑制剂常数（Ki）为0.2-0-4 mM。从腹水肿瘤细胞制备用于动力学研究的足够纯度的腺苷酸琥珀酸裂解酶。在存在和不存在6-硫代肌苷5[image]-磷酸的情况下，在pH 5-64至8-38的12个pH值下测量腺苷酸琥珀酸转化为腺苷5[image]-磷酸的最大速度和表观米氏常数。6-硫代肌苷5[image]-磷酸是一种竞争性抑制剂; Ki从pH 5.64时的0.8 mM降至pH 8.38时的0.1 mM。腺苷酸琥珀酸的Km在相同范围内从6 [mu]M增加到0.07 mM。在pH 8以下，最大速度（V）随H+离子浓度的降低而增加，其关系如下：[图像]其中[图像]为11.5微摩尔的腺苷酸琥珀酸裂解/分钟/mg蛋白质，[长划线]log K1为6-3。用来自酵母的腺苷酸琥珀酸裂解酶获得了类似的结果。通过比较埃利希腹水肿瘤细胞中脱氢酶、合成酶和裂解酶的活性和动力学参数，似乎这些活性中的第一种对6-硫代肌苷5[image]-β-磷酸盐（抑制药物6-巯基嘌呤的代谢产物）的抑制作用最敏感。
The apparent activities of adenylosuccinate synthetase, adenylosuccinate lyase and inosine 5[image]-phosphate dehydrogenase were measured in extracts of Ehrlich ascites tumor cells that had been kept at[long dash]15[degree] for periods up to 93 days. In extracts of fresh cells the activity of the synthetase was greater than that of the dehydrogenase and less than that of the lyase. Adenylosuccinate synthetase from the ascites tumor cells was freed of interfering activities and used in kinetic studies of adenylosuccinate synthesis. At pH 7.5 the Michaelis constant (Km) for guanosine 5[image]-tri-phosphate was 0.1 mM. the Km for L-aspartate was 0.05 mM and the Km for inosine 5[image]-phosphate was 0.03 mM. 6-Thioinosine 5[image]-phosphate was a non-competitive inhibitor of conversion of inosine 5[image]-phosphate into adenylosuccinate; the inhibitor constant (Ki) was 0.2-0-4 mM. Adenylosuccinate lyase of adequate purity for kinetic studies was prepared from the ascites tumor cells. Maximum velocities and apparent Michaelis constants for the conversion of adenylosuccinate into adenosine 5[image]-phosphate in the presence and absence of 6-thioinosine 5[image]-phosphate were measured at 12 pH values from pH 5-64 to 8-38. 6-Thioinosine 5[image]-phosphate was a competitive inhibitor; Ki decreased from 0.8 mM at pH 5.64 to 0.1 mM at pH 8.38. The Km for adenylosuccinate increased from 6 [mu]M to 0.07 mM in the same range. Below pH 8 the increase of maximum velocity (V) with decreasing H+ ion concentration was described by the relationship: [image] where [image] was 11.5 um-moles of adenylosuccinate cleaved/min/mg of protein and[long dash]log K1 was 6-3. Similar results were obtained with adenylosuccinate lyase from yeast. From a comparison of the activities and kinetic parameters of the dehydrogenase, synthetase and lyase in Ehrlich ascites tumor cells it seems likely that the first of these activities is the most sensitive to inhibition by 6-thioinosine 5[image]-phos-phate, a metabolite of the inhibitory drug 6-mercaptopurine.