Clickable NAD Analogues for Labeling Substrate Proteins of Poly(ADP-ribose) Polymerases
作者:Hong Jiang、Jun Hyun Kim、Kristine M. Frizzell、W. Lee Kraus、Hening Lin
DOI:10.1021/ja101588r
日期:2010.7.14
proteins PARPs modify. Here we report clickable NADanalogues that can be used to label PARP substrate proteins. The clickable NADanalogues have a terminal alkyne group which allows the conjugation of fluorescent or affinity tags to the substrate proteins. Using this method, PARP-1 and tankyrase-1 substrate proteins were labeled by a fluorescent tag and visualized on SDS-PAGE gel. Using a biotin affinity
Electrocatalytic NAD<sup>+</sup> reduction <i>via</i> hydrogen atom-coupled electron transfer
作者:Fengyuan Liu、Chunmei Ding、Shujie Tian、Sheng-Mei Lu、Chengcheng Feng、Dandan Tu、Yan Liu、Wangyin Wang、Can Li
DOI:10.1039/d2sc02691k
日期:——
dinucleotide cofactor (NAD(P)H) is regarded as an important energy carrier and charge transfer mediator. Enzyme-catalyzed NADPH production in natural photosynthesis proceeds via a hydride transfer mechanism. Selective and effective regeneration of NAD(P)H from its oxidized form by artificial catalysts remains challenging due to the formation of byproducts. Herein, electrocatalytic NADH regeneration and the reaction
烟酰胺腺嘌呤二核苷酸辅因子(NAD(P)H)被认为是重要的能量载体和电荷转移介体。自然光合作用中酶催化的 NADPH 产生是通过氢化物转移机制进行的。由于副产物的形成,通过人工催化剂从氧化形式选择性有效地再生 NAD(P)H 仍然具有挑战性。本文研究了电催化NADH再生以及金属和碳电极上的反应机理。我们发现生物活性 1,4-NADH 在 Cu、Fe 和 Co 电极上的选择性相对较高,且不会形成常见报道的 NAD 2副产物。相反,碳电极形成更多的NAD 2副产物。ADP-核糖被证实是NAD +裂解反应产生的副产物。基于H/D同位素效应和电子顺磁共振分析,提出NADH在这些金属电极上的形成是通过氢原子耦合电子转移(H ad CET)机制进行的,而不是直接电子转移和NAD˙ 碳电极上的自由基路径,产生更多副产物 NAD 2。这项工作揭示了与生物催化不同的电催化 NADH 再生机制。
Bovine CD38/NAD(+) glycohydrolase catalyzes the hydrolysis of NAD(+) to nicotinamide and ADP-ribose and the formation of cyclic ADP-ribose via a stepwise reaction mechanism. Our recent crystallographic study of its Michaelis complex and covalently-trapped intermediates provided insights into the modalities of substrate binding and the molecular mechanism of bCD38. The aim of the present work was to determine the precise role of key conserved active site residues (Trp118, Glu138, Asp147, Trp181 and Glu218) by focusing mainly on the cleavage of the nicotinamide-ribosyl bond. We analyzed the kinetic parameters of mutants of these residues which reside within the bCD38 subdomain in the vicinity of the scissile bond of bound NAD(+). To address the reaction mechanism we also performed chemical rescue experiments with neutral (methanol) and ionic (azide, formate) nucleophiles. The crucial role of Glu218, which orients the substrate for cleavage by interacting with the N-ribosyl 2'-OH group of NAD(+), was highlighted. This contribution to catalysis accounts for almost half of the reaction energy barrier. Other contributions can be ascribed notably to Glu138 and Asp147 via ground-state destabilization and desolvation in the vicinity of the scissile bond. Key interactions with Trp118 and Trp181 were also proven to stabilize the ribooxocarbenium ion-like transition state. Altogether we propose that, as an alternative to a covalent acylal reaction intermediate with Glu218, catalysis by bCD38 proceeds through the formation of a discrete and transient ribooxocarbenium intermediate which is stabilized within the active site mostly by electrostatic interactions. (C) 2014 Elsevier B.V. All rights reserved.
Pyridine nucleotide chemistry. A new mechanism for the hydroxide-catalyzed hydrolysis of the nicotinamide-glycosyl bond
作者:Randy W. Johnson、Thomas M. Marschner、Norman J. Oppenheimer