区域选择性芳族羟基化对于生产有价值的化合物是合乎需要的。外部含有黄素的单加氧酶通过烟酰胺腺嘌呤二核苷酸辅酶的黄素还原,随后与分子氧反应,活化并选择性地将氧原子掺入酚类化合物中。这项研究提供了辅酶仿生剂黄素酶催化选择性芳香族羟基化反应原理的证明。特别是氨基甲酰基甲基取代的仿生品可在不到两个小时的时间内实现5 mM 3-羟基和4-羟基苯甲酸酯的选择性羟基化的完全转化,显示出与NADH相似的速率,实现了药用产品龙胆酸酯的10 mM / h的酶促转化。这种仿生物似乎产生较少的羟基解偶联,这通常导致不希望的过氧化氢。因此,我们表明这些黄素酶具有与仿生剂结合应用的潜力。
Excited-state proton-coupled electron transfer within ion pairs
作者:Wesley B. Swords、Gerald J. Meyer、Leif Hammarström
DOI:10.1039/c9sc04941j
日期:——
means to study an ES-PCET mechanism. These ion pairs formed readily between salicylate anions and tetracationic rutheniumcomplexes in acetonitrile solution. Upon light excitation, quenching of the ruthenium excited state occurred through ES-PCET oxidation of salicylate within the ion pair. Transient absorption spectroscopy identified the reduced rutheniumcomplex and oxidized salicylate radical as the
Inhibition of chorismate-utilising enzymes by 2-amino-4-carboxypyridine and 4-carboxypyridone and 5-carboxypyridone analogues
作者:Richard J. Payne、Esther M. M. Bulloch、Olivier Kerbarh、Chris Abell
DOI:10.1039/c004062b
日期:——
chorismate-utilising enzyme family, anthranilatesynthase, isochorismatesynthase and salicylate synthase. Most compounds exhibited low micromolar inhibition of these three enzymes. The most potent inhibitor was a 4-carboxypyridone analogue bearing a lactate side chain on the pyridyl nitrogen which exhibited inhibition constants of 5, 91 and 54 μM against anthranilatesynthase, isochorismatesynthase and salicylate
with only a handful of biocatalysts available to this end. We have increased the spectrum of carboxylate-reducing enzymes (CARs) with the sequence of a fungal CAR fromNeurosporacrassa OR74A (NcCAR). NcCAR was efficiently expressed in E. coli using an autoinduction protocol at low temperature. It was purified and characterized in vitro, revealing a broad substrate acceptance, a pH optimum at pH 5.5-6
羧酸的酶促还原还处于初期,只有少数几种生物催化剂可用于此目的。我们已经利用来自神经孢霉OR74A(NcCAR)的真菌CAR的序列增加了羧酸盐还原酶(CARs)的谱图。NcCAR在低温下使用自动诱导方案在大肠杆菌中有效表达。对其进行了纯化和体外表征,显示了广泛的底物接受性,最适pH值为5.5-6.0,Tm为45°C和副产物焦磷酸盐的抑制作用(可通过添加焦磷酸酶来缓解)。NcCAR的合成效用已在使用大肠杆菌K-12 MG1655 RARE菌株进行全细胞生物转化中得到证实,目的是抑制过度还原为不想要的酒精。由戊酸(30 mM)以克规模制备芳香化合物胡椒醛,分离出的产率为92%,纯度> 98%。这对应于1.5g / L / h的生产率。
Isochorismate Pyruvate Lyase: A Pericyclic Reaction Mechanism?
作者:Michael S. DeClue、Kim K. Baldridge、Dominik E. Künzler、Peter Kast、Donald Hilvert
DOI:10.1021/ja055871t
日期:2005.11.1
highly asynchronous pericyclic transition structure, in which carbon-oxygen bond cleavage is more advanced than hydrogen atom transfer from C2 to C9; the calculated 2H isotope effect of 2.22 at C2 is in excellent accord with the experimental value. Together, these findings indicate that IPL should be added to the small set of proteins that are known to catalyze pericyclicreactions. They also raise the
Conversion of Anthranilate Synthase into Isochorismate Synthase: Implications for the Evolution of Chorismate-Utilizing Enzymes
作者:Maximilian G. Plach、Patrick Löffler、Rainer Merkl、Reinhard Sterner
DOI:10.1002/anie.201505063
日期:2015.9.14
Chorismate‐utilizing enzymes play a vital role in the biosynthesis of metabolites in plants as well as free‐living and infectious microorganisms. Among these enzymes are the homologous primary metabolic anthranilate synthase (AS) and secondary metabolic isochorismate synthase (ICS). Both catalyze mechanistically related reactions by using ammonia and water as nucleophiles, respectively. We report that