is able to form (S)‐acetoin with particularly high enantioselectivity (up to 95 % ee) by all three pathways. Mechanistic studies utilizing 13C‐labeled substrates revealed an unprecedented non‐acetolactate pathway for the homocoupling of pyruvate, which explains the high enantioselectivity in the CDH‐catalyzedformation of (S)‐acetoin.
α-Hydroxy-β-keto acid rearrangement–decarboxylation: impact on thiamine diphosphate-dependent enzymatic transformations
作者:Maryam Beigi、Sabrina Loschonsky、Patrizia Lehwald、Volker Brecht、Susana L. A. Andrade、Finian J. Leeper、Werner Hummel、Michael Müller
DOI:10.1039/c2ob26981c
日期:——
The thiamine diphosphate (ThDP) dependent MenD catalyzes the reaction of α-ketoglutarate with pyruvate to selectively form 4-hydroxy-5-oxohexanoic acid 2, which seems to be inconsistent with the assumed acyl donor role of the physiological substrate α-KG. In contrast the reaction of α-ketoglutarate with acetaldehyde gives exclusively the expected 5-hydroxy-4-oxo regioisomer 1. These reactions were studied by NMR and CD spectroscopy, which revealed that with pyruvate the observed regioselectivity is due to the rearrangementâdecarboxylation of the initially formed α-hydroxy-β-keto acid rather than a donorâacceptor substrate role variation. Further experiments with other ThDP-dependent enzymes, YerE, SucA, and CDH, verified that this degenerate decarboxylation can be linked to the reduced enantioselectivity of acyloins often observed in ThDP-dependent enzymatic transformations.
Extending the Spectrum of α-Dicarbonyl Compounds in Vivo
作者:Christian Henning、Kristin Liehr、Matthias Girndt、Christof Ulrich、Marcus A. Glomb
DOI:10.1074/jbc.m114.563593
日期:2014.10
Maillard alpha-dicarbonyl compounds are known as central intermediates in advanced glycation end product (AGE) formation. Glucose is the primary source of energy for the human body, whereas l-threo-ascorbic acid (vitaminC) is an essential nutrient, involved in a variety of enzymatic reactions. Thus, the Maillarddegradation of glucose and ascorbic acid is of major importance in vivo. To understand
Photochemistry of pyruvic acid is governed by photo-induced intermolecular electron transfer through hydrogen bonds
作者:Jennifer S. Lewis、Adam P. Gaunt、Arnaud Comment
DOI:10.1039/d2sc03038a
日期:——
electron transfer occurs via hydrogen bonding and that in aqueous solutions of pyruvicacid, the hydrated form is the electron acceptor. These findings demonstrate that photo-induced electron transfer via hydrogen bonding can occur between two simple carboxylic acids and that this mechanism governs the photochemistry of pyruvicacid, providing unexplored alternative pathways for the decarboxylation of photo-inactive
尽管进行了超过 85 年的研究,丙酮酸光脱羧背后的机制仍然难以捉摸。大多数研究都集中在丙酮酸稀释溶液的气相和液相上,以了解阳光对该分子在大气中降解的影响。通过分析 77 K 的浓缩过冷溶液,我们证明丙酮酸分子不是脱羧,而是扮演电子供体的角色,并将电子转移到受体分子,受体分子随后降解形成 CO 2。我们表明这种电子转移是通过氢键发生的,并且在丙酮酸的水溶液中,水合形式是电子受体。这些发现表明,光诱导电子转移通过氢键可以发生在两个简单的羧酸之间,这种机制控制着丙酮酸的光化学,为光惰性分子的脱羧提供了未探索的替代途径。
The origin of the β-lactam carbons of clavulanic acid
作者:Jan E. Thirkettle、Jack E. Baldwin、Jeff Edwards、John P. Griffin、Christopher J. Schofield
DOI:10.1039/a701934c
日期:——
Pyruvate is the most likely primary metabolic source of the three
β-lactam carbons of clavulanic acid.