Inhibition of the PLP-dependent enzyme serine palmitoyltransferase by cycloserine: evidence for a novel decarboxylative mechanism of inactivation.
Inhibition of the PLP-dependent enzyme serine palmitoyltransferase by cycloserine: evidence for a novel decarboxylative mechanism of inactivation.
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DOI：
10.1039/c003743e
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发表时间：
2010-09
影响因子：
--
通讯作者：
Campopiano DJ
中科院分区：
文献类型：
--
作者：
Lowther J;Yard BA;Johnson KA;Carter LG;Bhat VT;Raman MC;Clarke DJ;Ramakers B;McMahon SA;Naismith JH;Campopiano DJ
环丝氨酸（CS， 4-氨基-3-异唑烷酮）是一种环氨基酸模拟物，已知可抑制许多必需的吡哆醛5 ' -磷酸（PLP）依赖性酶。已知两种CS对映体；d-环丝氨酸（DCS，也称为丝霉素）是一种天然产物，用于治疗耐药结核分枝杆菌感染以及神经系统疾病，因为它是一种有效的NMDA受体激动剂，而l-环丝氨酸（LCS）是一种合成对构象，其作为药物的用途由于其抑制鞘脂代谢而产生的固有毒性而受到阻碍。先前对多种plp依赖性酶的研究揭示了CS的两种对映体的共同抑制机制；PLP辅因子通过在环丝氨酸环保持完整的活性位点形成稳定的3-羟基异恶唑/吡哆胺5 ' -磷酸（PMP）加合物而失活。本文描述了少动鞘单胞菌plp依赖性丝氨酸棕榈酰转移酶（SPT）的CS失活的新机制。SPT催化l-丝氨酸和棕榈酰辅酶a的缩合，这是鞘脂生物合成新途径的第一步。我们使用了一系列动力学、光谱和结构技术来假设LCS和DCS都通过转氨化作用使SPT失活，形成游离的吡哆胺5 ' -磷酸（PMP）和β-氨基乙醛，它们仍然结合在活性位点。我们认为这是通过环丝氨酸环开环然后脱羧发生的。酶动力学表明，与过量PLP孵育后抑制作用被逆转，LCS是比DCS更有效的SPT抑制剂。紫外可见光谱数据，结合定点诱变，表明一个可移动的Arg378残基参与了SPT环丝氨酸失活。
Cycloserine (CS, 4-amino-3-isoxazolidone) is a cyclic amino acid mimic that is known to inhibit many essential pyridoxal 5′-phosphate (PLP)-dependent enzymes. Two CS enantiomers are known; d-cycloserine (DCS, also known as Seromycin), is a natural product that is used to treat resistant Mycobacterium tuberculosis infections as well as neurological disorders since it is a potent NMDA receptor agonist, and l-cycloserine (LCS), is a synthetic enantiomer whose usefulness as a drug has been hampered by its inherent toxicity arising through inhibition of sphingolipid metabolism. Previous studies on various PLP-dependent enzymes revealed a common mechanism of inhibition by both enantiomers of CS; the PLP cofactor is disabled by forming a stable 3-hydroxyisoxazole/pyridoxamine 5′-phosphate (PMP) adduct at the active site where the cycloserine ring remains intact. Here we describe a novel mechanism of CS inactivation of the PLP-dependent enzyme serine palmitoyltransferase (SPT) from Sphingomonas paucimobilis. SPT catalyses the condensation of l-serine and palmitoyl-CoA, the first step in the de novo sphingolipid biosynthetic pathway. We have used a range of kinetic, spectroscopic and structural techniques to postulate that both LCS and DCS inactivate SPT by transamination to form a free pyridoxamine 5′-phosphate (PMP) and β-aminooxyacetaldehyde that remain bound at the active site. We suggest this occurs by ring opening of the cycloserine ring followed by decarboxylation. Enzyme kinetics show that inhibition is reversed by incubation with excess PLP and that LCS is a more effective SPT inhibitor than DCS. UV-visible spectroscopic data, combined with site-directed mutagenesis, suggest that a mobile Arg378 residue is involved in cycloserine inactivation of SPT.
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DOI：
10.1073/pnas.0811269106
发表时间：
2009-05-19
影响因子：
11.1
作者：
Han, Gongshe;Gupta, Sita D.;Dunn, Teresa M.
通讯作者：
Dunn, Teresa M.
DOI：
10.1107/s0907444904019158
发表时间：
2004-12-01
影响因子：
2.2
作者：
Emsley, P;Cowtan, K
通讯作者：
Cowtan, K
影响因子：
2.9
作者：
Fenn, TD;Holyoak, T;Ringe, D
通讯作者：
Ringe, D
影响因子：
5.6
作者：
Jahan, Nasrin;Potter, Jane A.;Taylor, Garry L.
通讯作者：
Taylor, Garry L.
影响因子：
2.9
作者：
Brandt, Gabriel S.;Nemeria, Natalia;Ringe, Dagmar
通讯作者：
Ringe, Dagmar