Gorle Anil Kumar, Rajaratnam Premraj, Chang Chih-Wei, von Itzstein Mark, Berners-Price Susan J, Farrell Nicholas P
Institute for Glycomics , Griffith University, Gold Coast Campus , Southport , Queensland 4222 , Australia.
Department of Chemistry , Virginia Commonwealth University , Richmond , Virginia 23284 , United States.
Inorg Chem. 2019 Jun 3;58(11):7146-7155. doi: 10.1021/acs.inorgchem.8b03035. Epub 2019 Jan 11.
We report herein a detailed NMR study of the aquation and subsequent covalent binding of the trinuclear clinical agent [{ trans-PtCl(NH)}{μ- trans-Pt(NH)(NH(CH)NH)}] (1, 1,0,1/ t, t, t or Triplatin) with three d-glucosamine residues containing varied O-sulfate and N-sulfate or N-acetyl substitutions, which represent monosaccharide fragments present within the repeating disaccharide sequences of cell surface heparan sulfate (HS). The monosaccharides GlcNS(6S), GlcNS, and GlcNAc(6S) were synthesized in good yield from a common 4,6-diol α-methyl glucopyranoside intermediate. The reactions of N-1 with sodium sulfate, GlcNS(6S), GlcNS, and GlcNAc(6S) were followed by 2D [H,N] heteronuclear single quantum coherence (HSQC) NMR spectroscopy using conditions (298 K, pH ≈5.4) similar to those previously used for other anionic systems, allowing for a direct comparison. The equilibrium constants (p K) for the aquation of 1 in the presence of GlcNS(6S) and GlcNS were slightly higher compared to that of the aquation in a sulfate solution, while a comparable p K value was observed in the presence of GlcNAc(6S). A comparison of the rate constants for sulfate displacement of the aqua ligand showed preferential binding to 2- N-sulfate compared to 6- O-sulfate but a more rapid liberation. For disulfated GlcNS(6S), equilibrium conditions were achieved rapidly (9 h) and strongly favored the dichloro form, with <2% sulfato species observed. The value of k was up to 15-fold lower than that for binding to sulfate, whereas the rate constant for the reverse ligation ( k) was comparable. Equilibrium conditions were achieved much more slowly (∼ 100 h) for the reactions of 1 with GlcNS and GlcNAc(6S), attributed to covalent binding also to the N-donor of the sulfamate (GlcNS) group and the O-donor of the N-acetyl [GlcNAc(6S)] group. The rate constants ( k) were 20-40-fold lower than that for binding to the 2- N- or 6- O-sulfate, but the binding was less reversible, so that their equilibrium concentrations (5-8%) were comparable to the 2- N- or 6- O-sulfate-bound species. The results emphasize the relevance of glycans in bioinorganic chemistry and underpin a fundamental molecular description of the HS-Pt interactions that alter the profile of platinum agents from cytotoxic to metastatic in a systematic manner.
我们在此报告了一项详细的核磁共振（NMR）研究，该研究涉及三核临床药物[{反式-PtCl(NH)}{μ-反式-Pt(NH)(NH(CH)NH)}]（1，1,0,1/t，t，t或三铂）与三个含有不同O-硫酸盐、N-硫酸盐或N-乙酰基取代的d-葡萄糖胺残基的水合作用及随后的共价结合，这些残基代表细胞表面硫酸乙酰肝素（HS）重复二糖序列中存在的单糖片段。单糖GlcNS(6S)、GlcNS和GlcNAc(6S)由常见的4,6-二醇α-甲基吡喃葡萄糖苷中间体高产率合成。N-1与硫酸钠、GlcNS(6S)、GlcNS和GlcNAc(6S)的反应通过二维[H,N]异核单量子相干（HSQC）核磁共振光谱进行跟踪，使用的条件（298K，pH≈5.4）与先前用于其他阴离子系统的条件相似，以便进行直接比较。与在硫酸盐溶液中的水合作用相比，在GlcNS(6S)和GlcNS存在下1的水合作用的平衡常数（pK）略高，而在GlcNAc(6S)存在下观察到相当的pK值。水合配体的硫酸盐取代速率常数的比较表明，与6-O-硫酸盐相比，优先与2-N-硫酸盐结合，但释放更快。对于双硫酸化的GlcNS(6S)，平衡条件迅速达到（9小时），并且强烈有利于二氯形式，观察到的硫酸根物种<2%。k值比与硫酸盐结合的值低至15倍，而反向连接的速率常数（k）相当。1与GlcNS和GlcNAc(6S)反应的平衡条件达到得要慢得多（约100小时），这归因于与氨基磺酸酯（GlcNS）基团的N供体和N-乙酰基[GlcNAc(6S)]基团的O供体的共价结合。速率常数（k）比与2-N-或6-O-硫酸盐结合的值低20-40倍，但结合的可逆性较小，因此它们的平衡浓度（5-8%）与2-N-或6-O-硫酸盐结合的物种相当。结果强调了聚糖在生物无机化学中的相关性，并为HS-Pt相互作用提供了基本的分子描述，这种相互作用以系统的方式改变了铂类药物从细胞毒性到转移性的特征。
