使用高级 ab initio 分子轨道计算的结果讨论了 (S)-谷氨酸和 (2S,3S)-3-甲基天冬氨酸的相互转化,由 B(12) 依赖性谷氨酸变位酶催化。提供了关于辅酶-B(12) 在底物激活和通过自由基生成的产物形成中的可能作用的证据。计算出的电子顺磁共振参数支持底物衍生自由基参与的实验证据,并有望帮助未来检测其他重要的自由基中间体。使用包括迁移甘氨酰基中的中性氨基和羧酸取代基的模型计算的断裂-重组途径的重排屏障的高度支持了(S)-谷氨酸和(2S,3S)-3-甲基天冬氨酸通过这样的途径。我们的计算表明,该酶可能通过控制迁移基团中取代基的质子化状态的(部分)质子转移过程促进(S)-谷氨酸的重排。
Stereochemical Recognition of Doubly Functional Aminotransferase in 2-Deoxystreptamine Biosynthesis
摘要:
The doubly functional aminotransferase BtrS in the 2-deoxystreptamine (DOS) biosynthesis, in which two transaminations are involved, was characterized by a genetic as well as a chemical approach with the heterologously expressed enzyme. The gene disruption study clearly showed that BtrS is involved, in addition to the previously confirmed first transamination, in the second transamination as well. This dual function of BtrS for the DOS biosynthesis was further confirmed by the structural determination of the reverse reaction product from DOS. Enantiospecific formation of the reverse reaction product from DOS clearly showed that BtrS distinguishes the enantiotopic amino groups of DOS, but in contrast, both enantiomers of 2-deoxy-scyllo-inosose (DOI) were efficiently accepted by BtrS to give a racemic product. This unique stereochemical recognition of DOI chirality and DOS prochirality by BtrS is mechanistically explained by a specific hydrogen-bond donating force in the enzyme active site as a particular feature of this doubly functional enzyme.
Glutamate decarboxylase (GAD) from the archaeon Pyrococcus horikoshii was successfully expressed and purified, with the aim of developing a hyperthermostable GAD for industrial applications. Its biochemical properties were different from those reported for other GADs. The enzyme had broad substrate specificity, and its optimum pH and temperature were pH 8.0 and >97 °C.
A Remarkable Oxidative Cascade That Replaces the Riboflavin C8 Methyl with an Amino Group during Roseoflavin Biosynthesis
作者:Isita Jhulki、Prem K. Chanani、Sameh H. Abdelwahed、Tadhg P. Begley
DOI:10.1021/jacs.6b02469
日期:2016.7.13
Roseoflavin is a naturally occurring riboflavin analogue with antibiotic properties. It is biosynthesized from riboflavin in a reaction involving replacement of the C8 methyl with a dimethylamino group. Herein we report the identification of a flavin-dependent enzyme that converts flavin mononucleotide (FMN) and glutamate to 8-amino-FMN via the intermediacy of 8-formyl-FMN. A mechanistic proposal for
An investigation of the equilibrium of the reaction {L-aspartate(aq)+2-oxoglutarate(aq)=oxaloacetate(aq)+L-glutamate(aq)}
作者:Nand Kishore、Yadu B. Tewari、Robert N. Goldberg
DOI:10.1006/jcht.1998.0404
日期:1998.11
accompanied the reaction. Values of ΔRwere measured for several solutions under near equilibrium conditions. The chromatographic response ΔRis expected to be zero for a solution that is at equilibrium with regard to the above reaction and prior to the addition of the enzyme. The results were used to calculate the standard molar Gibbs energy change ΔrGm°=(4.82±0.21) kJ·mol−1, the equilibrium constantK=(0
Thermodynamic studies about the interaction of scorpiand aza-macrocycles with amino acids in water show entropy driven stabilisations often associated with solvation/desolvation processes.
在水中关于蝎烯和氮杂大环与氨基酸相互作用的热力学研究表明,熵驱动的稳定化通常与溶解/脱溶过程相关。
A Previously Unrecognized Kanosamine Biosynthesis Pathway in <i>Bacillus subtilis</i>
作者:Natasha D. Vetter、David M. Langill、Shazia Anjum、Julie Boisvert-Martel、Rajendra C. Jagdhane、Egiroh Omene、Hongyan Zheng、Karin E. van Straaten、Isaac Asiamah、Ed S. Krol、David A. R. Sanders、David R. J. Palmer
DOI:10.1021/ja4010255
日期:2013.4.24
NtdC, constitute a complete set of enzymes required for NTD synthesis, although their functions have never been demonstrated in vitro. We now report that these enzymes catalyze the biosynthesis of kanosamine from glucose-6-phosphate: NtdC is a glucose-6-phosphate 3-dehydrogenase, NtdA is a pyridoxal phosphate-dependent 3-oxo-glucose-6-phosphate:glutamate aminotransferase, and NtdB is a kanosamine-6-phosphate