Enzymatic Birch Reduction via Hydrogen Atom Transfer at an Aqua-Tungsten- bis-Metallopterin Cofactor

The Birch reduction is a widely used synthetic tool to reduce arenes to 1,4-cyclohexadienes. Its harsh cryogenic reaction conditions and the dependence on alkali metals have motivated researchers to explore alternative approaches. In anaerobic aromatic compound degrading microbes, class II benzoyl-coenzyme A (CoA) reductases (BCRs) reduce...

The rates of Cu(ii)-ATCUN complex formation. Why so slow?

We used a series of modified/substituted GGH analogues to investigate the kinetics of Cu(ii) binding to ACTUN peptides. Rules for rate modulation by 1^st and 2^nd sphere interactions were established, providing crucial insight into elucidation of the reaction mechanism and its contribution to biological copper transport.

Unique Biradical Intermediate in the Mechanism of the Heme Enzyme Chlorite Dismutase

The heme enzyme chlorite dismutase (Cld) catalyzes O-O bond formation as part of the conversion of the toxic chlorite (ClO2-) to chloride (Cl-) and molecular oxygen (O2). Enzymatic O-O bond formation is rare in nature, and therefore, the reaction mechanism of Cld is of great interest. Microsecond timescale pre-steady-state kinetic experiments...

Correction to: A traffic light enzyme: acetate binding reversibly switches chlorite dismutase from a red- to a green-colored heme protein (JBIC Journal of Biological Inorganic Chemistry, (2020), 25, 4, (609-620), 10.1007/s00775-020-01784-1)

In the original article published, in the g_y value (column) of the H₂O/OH⁻species (row) of Table 2 was mistakenly given as “1.18” and the correct value is “2.18”.

Key Intermediate Species Reveal the Copper(II)-Exchange Pathway in Biorelevant ATCUN/NTS Complexes

The amino-terminal copper and nickel/N-terminal site (ATCUN/NTS) present in proteins and bioactive peptides exhibits high affinity towards Cu^II ions and have been implicated in human copper physiology. Little is known, however, about the rate and exact mechanism of formation of such complexes. We used the stopped-flow and...

A traffic light enzyme: acetate binding reversibly switches chlorite dismutase from a red- to a green-colored heme protein

Abstract: Chlorite dismutase is a unique heme enzyme that catalyzes the conversion of chlorite to chloride and molecular oxygen. The enzyme is highly specific for chlorite but has been known to bind several anionic and neutral ligands to the heme iron. In a pH study, the enzyme changed color from red to green in acetate buffer pH 5.0. The...

Microsecond time-scale kinetics of transient biochemical reactions

To afford mechanistic studies in enzyme kinetics and protein folding in the microsecond time domain we have developed a continuous-flow microsecond time-scale mixing instrument with an unprecedented dead-time of 3.8 ± 0.3 μs. The instrument employs a micro-mixer with a mixing time of 2.7 μs integrated with a 30 mm long flow-cell of 109 μm...

Electron tunneling rates in respiratory complex I are tuned for efficient energy conversion

Respiratory complex I converts the free energy of ubiquinone reduction by NADH into a proton motive force, a redox reaction catalyzed by flavin mononucleotide(FMN) and a chain of seven iron–sulfur centers. Electron transfer rates between the centers were determined by ultrafast freezequenching and analysis by EPR and UV/Vis spectroscopy. The...

Electron Tunneling Rates in Respiratory Complex?I Are Tuned for Efficient Energy Conversion

Respiratory complex I converts the free energy of ubiquinone reduction by NADH into a proton motive force, a redox reaction catalyzed by flavin mononucleotide(FMN) and a chain of seven iron–sulfur centers. Electron transfer rates between the centers were determined by ultrafast freeze-quenching and analysis by EPR and UV/Vis spectroscopy. The...

Die Elektronentunnelraten im Atmungskettenkomplex I sind auf eine effiziente Energiewandlung abgestimmt

Der Atmungskettenkomplex I wandelt die freie Energie, die bei der Reduktion von Ubichinon durch NADH frei wird, in einen Protonengradienten über die Membran um. Die biologische Redoxreaktion wird von einem Flavinmononukleotid und einer Kette von sieben Eisen-Schwefel-Zentren katalysiert. Die Elektronentransfergeschwindigkeiten zwischen den...