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Results for “Redox-Active Enzymes”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Nanotube-Supported Phospholipid Bilayers (Final Technical Report)

The overarching goal of this project was to attain fundamental understanding of structural organization, self-assembly, and function of redox-active enzymes and biological energy transduction systems localized at biological (cellular membranes) as well as manmade bio-nano interfaces. During this project we developed (1) nanopore surfaces suitable to stabilization of functional redox active enzymes and (2) experimental protocols for loading for loading of redox active enzymes into nanopores and taking advantage of self-assembly for forming layer(s) of redox active enzymes inside the nanochannels formed in anodic aluminum oxide (AAO) substrates.

14 SOLAR ENERGY↗
DOE OSTI2024

Structure-driven development of a biomimetic rare earth artificial metalloprotein

The 2011 discovery of the first rare earth–dependent enzyme in methylotrophic Methylobacterium extorquens AM1 prompted intensive research toward understanding the unique chemistry at play in these systems. This enzyme, an alcohol dehydrogenase (ADH), features a La 3+ ion closely associated with redox-active coenzyme pyrroloquinoline quinone (PQQ) and is structurally homologous to the Ca 2+ -dependent ADH from the same organism. AM1 also produces a periplasmic PQQ-binding protein, PqqT, which we have now structurally characterized to 1.46-Å resolution by X-ray diffraction. This crystal structure reveals a Lys residue hydrogen-bonded to PQQ at the site analogously occupied by a Lewis acidic cation in ADH. Accordingly, we prepared K 142 A- and K 142 D-PqqT variants to assess the relevance of this site toward metal binding. Isothermal titration calorimetry experiments and titrations monitored by UV–Vis absorption and emission spectroscopies support that K 142 D-PqqT binds tightly (Kd = 0.6 ± 0.2 μM) to La 3+ in the presence of bound PQQ and produces spectral signatures consistent with those of ADH enzymes. These spectral signatures are not observed for WT- or K 142 A-variants or upon addition of Ca 2+ to PQQ ⸦ K 142 D-PqqT. Addition of benzyl alcohol to La 3+ -bound PQQ ⸦ K 142 D-PqqT (but not Ca 2+ -bound PQQ ⸦ K 142 D-PqqT, or La 3+ -bound PQQ ⸦ WT-PqqT) produces spectroscopic changes associated with PQQ reduction, and chemical trapping experiments reveal the production of benzaldehyde, supporting ADH activity. By creating a metal binding site that mimics native ADH enzymes, we present a rare earth-dependent artificial metalloenzyme primed for future mechanistic, biocatalytic, and biosensing applications.

Science & Technology - Other Topics↗
DOE OSTI2024

Electron transfer in polysaccharide monooxygenase catalysis

Polysaccharide monooxygenase (PMO) catalysis involves the chemically difficult hydroxylation of unactivated C–H bonds in carbohydrates. The reaction requires reducing equivalents and will utilize either oxygen or hydrogen peroxide as a cosubstrate. Two key mechanistic questions are addressed here: 1) How does the enzyme regulate the timely and tightly controlled electron delivery to the mononuclear copper active site, especially when bound substrate occludes the active site? and 2) How does this electron delivery differ when utilizing oxygen or hydrogen peroxide as a cosubstrate? Using a computational approach, potential paths of electron transfer (ET) to the active site copper ion were identified in a representative AA9 family PMO from Myceliophthora thermophila ( Mt PMO9E). When Y62, a buried residue 12 Å from the active site, is mutated to F, lower activity is observed with O 2 . However, a WT-level activity is observed with H 2 O 2 as a cosubstrate indicating an important role in ET for O 2 activation. To better understand the structural effects of mutations to Y62 and axial copper ligand Y168, crystal structures were solved of the wild type Mt PMO9E and the variants Y62W, Y62F, and Y168F. A bioinformatic analysis revealed that position 62 is conserved as either Y or W in the AA9 family. The Mt PMO9E Y62W variant has restored activity with O 2 . Overall, the use of redox-active residues to supply electrons for the reaction with O 2 appears to be widespread in the AA9 family. Furthermore, the results provide a molecular framework to understand catalysis with O 2 versus H 2 O 2 .

Sayler, Richard I. (ORCID:000000017252707X)↗