A kinetic study of the soluble 5'-nucleotidase of rat liver.
A kinetic study of the soluble 5'-nucleotidase of rat liver.
复制标题
大鼠肝脏可溶性5-核苷酸酶的动力学研究。
DOI：
10.1042/bj1620611
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发表时间：
1977
期刊：
影响因子：
--
通讯作者：
H. Hers
中科院分区：
文献类型：
--
作者：
G. van den Berghe;C. van Pottelsberghe;H. Hers
1.研究了存在于大鼠肝胞质溶胶中的5 '-核苷酸酶（EC 3.1.3.5）与腺嘌呤核苷酸转化为尿酸的关系的动力学性质，特别是果糖对该过程的刺激。通过Pi的释放和一种新的、更灵敏的放射化学方法来测定该酶。2.当IMP用作底物时，部分纯化的酶显示几乎双曲线动力学（h = 1.1），S0.5 = 1.2 mM。3. Vmax。AMP的酶活力与IMP的酶活力基本相同，但动力学为S形（h = 1.6），S 0.5 = 10 mM。GMP竞争性抑制IMP的水解。IMP，在浓度高达0.5 mM，有一个矛盾的刺激作用的水解2-5 mM-AMP和抑制在更高的浓度。5. ATP和GTP对该酶的AMP和IMP活性有促进作用，而Pi则对该酶的AMP和IMP活性有抑制作用。激活剂和抑制剂的作用大致相互抵消。在pH7.4时，在生理条件下，用0. 2 mM-AMP不能检测到酶活性。6.可以得出结论，在肝细胞中，AMP不被可溶性5 '-核苷酸酶水解，但其降解需要预先脱氨基为IMP。
1. The kinetic properties of the 5'-nucleotidase (EC 3.1.3.5) present in the cytosol of rat liver were investigated in relation to the conversion of adenine nucleotides into uric acid, with particular reference to the stimulation of this process by fructose. The enzyme was assayed by the release of Pi and by a new and more sensitive radiochemical procedure. 2. When IMP was used as substrate, the partially purified enzyme displayed almost hyperbolic kinetics (h = 1.1) with S0.5 = 1.2 mM. Similar kinetics were observed with GMP and other nucleoside 5'-monophosphates, except AMP. 3. Vmax. of the enzyme for AMP was about the same as for IMP, but the kinetics were sigmoidal (h = 1.6) with S 0.5 = 10 mM. 4. The hydrolysis of IMP was inhibited competitively by GMP. IMP, at concentrations up to 0.5 mM, had a paradoxical stimulatory action on the hydrolysis of 2-5 mM-AMP and was inhibitory at higher concentrations. 5. The activity of the enzyme towards AMP and IMP was stimulated by ATP and GTP, and inhibited by Pi. Activators and inhibitor approximately cancelled each others' effects. At pH 7.4, the enzymic activity with 0.2 mM-AMP was undetectable under physiological conditions. 6. It is concluded that, in the liver cell, AMP is not hydrolysed by the soluble 5'-nucleotidase, but that its degradation requires prior deamination to IMP.