SPECIFICITY OF S-ADENOSYLMETHIONINE SYNTHETASE FOR ATP ANALOGS MONOSUBSTITUTED AND DISUBSTITUTED IN BRIDGING POSITIONS OF THE POLYPHOSPHATE CHAIN
SPECIFICITY OF S-ADENOSYLMETHIONINE SYNTHETASE FOR ATP ANALOGS MONOSUBSTITUTED AND DISUBSTITUTED IN BRIDGING POSITIONS OF THE POLYPHOSPHATE CHAIN
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DOI：
10.1021/bi00458a011
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发表时间：
1990-02-13
期刊：
影响因子：
2.9
通讯作者：
MARKHAM, GD
中科院分区：
文献类型：
--
作者：
MA, QF;KENYON, GL;MARKHAM, GD
在ATP的多磷酸链中被亚氨基和亚甲基桥单取代或双取代的整个ATP类似物家族已被研究为S-腺苷甲硫氨酸合成酶（ATP：L-甲硫氨酸S-腺苷转移酶）的底物和抑制剂。二取代的类似物腺苷5“-（α-. beta.：.例如β，γ-二亚氨基三磷酸）（AMPNPNP）和腺苷5“-（α：. beta..α，.β的“-二亚氨基磷酸）[AMP（NP）2]的合成，并为腺苷5”-（α，. beta.：.例如β，γ-二亚甲基三磷酸盐（AMPCPCP）。S-腺苷甲硫氨酸合成酶催化一个两步反应：完整的多磷酸链从ATP中被置换，产生三磷酸甲硫氨酸和三聚磷酸，然后通常但不是必须的，三聚磷酸水解为焦磷酸和正磷酸。一致地，亚氨基单取代或双取代衍生物是比它们的亚甲基对应物更好的底物和更好的抑制剂。AMPNPNP反应迅速，每个活性位点产生一当量的产物，但随后的周转至少慢1000倍，使其能够用于定量酶活性位点浓度。相比之下，AMPNPNP不是底物，而是线性竞争性抑制剂，比ADP强> 100倍，表明在α-ADP下具有合理程度的整体耐受性。磷酰基结合位点。腺苷5“-（α，.β-的亚氨三磷酸）（AMPNPP）是一种令人惊讶的有效抑制剂以及底物，其抑制常数为λ。60-比ATP的Km小1倍，并且是约1000-比腺苷5 ″-（α，.贝塔亚甲基三磷酸）（AMPCPP）。这些发现强化了ATP的亚氨基类似物比其相应的亚甲基化合物更适合ATP类似物的概念。
The entire family of ATP analogues that are either mono- or disubstituted with imido and methylene bridges in the polyphosphate chain of ATP have been investigated as substrates and inhibitors of S-adensylmethionine synthetase (ATP:L-methionine S-adenosyltransferase). The disubstituted analogues adenosine 5''-(.alpha.-.beta.:.beta., .gamma.-diimidotriphosphate) (AMPNPNP) and adenosine 5''-(.alpha.:.beta..alpha.,.beta.''-diimidotrophosphate) [AMP(NP)2] have been synthesized for the first time, and a new route to adenosine 5''-(.alpha.,.beta.:.beta., .gamma.-dimethylenetriphosphate) (AMPCPCP) has been developed. S-adenosylmethionine synthetase catalyzes a two-step reaction: the intact polyphosphate chain is displaced from ATP, yielding AdoMet and tripolyphosphate, followed normally, but not obligatory, by the hydrolysis of the tripolyphosphate to pyrophosphate and orthophosphate. Uniformly, the imido mono-or disubstituted derivatives are both better substrates and better inhibitors than their methylene counterparts. AMPNPNP reacts rapidly to give a single equivalent of product per active site, but subsequent turnovers are at least 1000-fold slower, enabling it to be used to quantify enzyme active site concentrations. In contrast, AMPNPNP, was not a substrate but was a linear competitive inhibitor, > 100 fold more potent than ADP, indicating a reasonable degree of bulk tolerance at the .alpha.-phosphoryl group binding site. Asenosine 5''-(.alpha.,.beta.-imidotriphosphate) (AMPNPP) is a suprising potent inhibitor as well as substrate, with an inhibition constant that is .apprx. 60-fold less than the Km for ATP, and is an .apprx. 1000-fold better inhibitor than adenosine 5''-(.alpha.,.beta.-methylenetriphosphate) (AMPCPP). These findings reinforce the notion that imido analogues of ATP are more suitable analogues of ATP than their corresponding methylene compounds.