Topic
Substrate (chemistry)
About: Substrate (chemistry) is a research topic. Over the lifetime, 35902 publications have been published within this topic receiving 740722 citations. The topic is also known as: enzyme substrate.
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TL;DR: Results are consistent with a concerted mechanism involving direct side-on insertion of an active singlet "oxene" from the activated copper cluster across the "C-H" bond in the active site, and a possible role for the two reductants in the turnover of the enzyme is proposed.
Abstract: The particulate methane monooxygenase (pMMO) is a complex membrane protein complex that has been difficult to isolate and purify for biochemical and biophysical characterization because of its instability in detergents used to solubilize the enzyme. In this perspective, we summarize the progress recently made toward obtaining a purified pMMO−detergent complex and characterizing the enzyme in pMMO-enriched membranes. The purified pMMO is a multi-copper protein, with ca. 15 copper ions sequestered into five trinuclear copper clusters: two for dioxygen chemistry and alkane hydroxylation (catalytic or C-clusters) and three to provide a buffer of reducing equivalents to re-reduce the C-clusters following turnover (electron transfer or E-clusters). The enzyme is functional when all the copper ions are reduced. When the protein is purified under ambient aerobic conditions in the absence of a hydrocarbon substrate, only the C-clusters are oxidized; there is an apparent kinetic barrier for electron transfer from ...
146 citations
TL;DR: It is demonstrated that the carboxamidomethylated enzyme is a good model for the reduced species and the residues involved in glutathione binding as well as the geometry of the disulfide exchange are clearly shown.
Abstract: The binding of glutathione, some related molecules and two redox compounds to crystals of glutathione reductase has been investigated by X-ray crystallography at 0.3-nm resolution. Models for several bound ligands have been built and subjected to crystallographic refinement. The results clearly show the residues involved in glutathione binding as well as the geometry of the disulfide exchange. Glutathione-I is bound in a V-shaped conformation, while glutathione-II is extended. The zwitterionic glutamyl end of glutathione-II appears to be the most tightly bound part of the substrate. All glutathione conjugates and derivatives studied show binding dominated by the interactions at this site. In the reduced enzyme, glutathione-I forms a mixed disulfide intermediate with Cys58. Other structural changes are observed on reduction of the enzyme, and it is demonstrated that the carboxamidomethylated enzyme is a good model for the reduced species. Lipoate, a weak substrate of the enzyme, assumes a defined binding site where its disulfide is available for being attacked by Cys58-Sγ. A second region with affinity for a number of compounds has been found in a large cavity at the dimer interface of the enzyme. No functional role of this site is known.
146 citations
TL;DR: Although the two cyclic nucleotide-dependent protein kinases have similar substrate specificities, the determinants dictated by the primary sequence around the two phosphorylation sites in histone H2B are different for the two enzymes.
146 citations
TL;DR: In this paper, a gas-tight palladium membrane was prepared by the counter-diffusion chemical vapor deposition (CVD) process employing palladium chloride (PdCl2) vapor and H2 as Pd precursors.
146 citations
TL;DR: It is concluded that aortic lysyl oxidase is a copper metalloenzyme that catalyzed the formation of tritiated water from embryonic aortas grown in organ culture.
145 citations