Ethanolamine ammonia-lyase (EAL) catalyzes the adenosylcobalamin-dependent conversion of ethanolamine to acetaldehyde and ammonia. The wild-type enzyme shows a very low solubility. N-terminal truncation of the Escherichia coli EAL beta-subunit dramatically increases the solubility of the enzyme without altering its catalytic properties. Two deletion mutants of the enzyme [EAL(betaDelta4-30) and EAL(betaDelta4-43)] have been overexpressed, purified and crystallized using the sitting-drop vapour-diffusion method. Crystals of EAL(betaDelta4-30) and EAL(betaDelta4-43) diffracted to approximately 8.0 and 2.1 A resolution, respectively.
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| http://dx.doi.org/10.1107/S1744309110014478 | DOI Listing |
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Spectroscopic and Computational Insights into the Mechanism of Cofactor Cobalt-Carbon Bond Homolysis by the Adenosylcobalamin-Dependent Enzyme Ethanolamine Ammonia-Lyase.
J Am Chem Soc
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Department of Chemistry, University of Wisconsin─Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States.
The adenosylcobalamin (AdoCbl)-dependent enzyme ethanolamine ammonia-lyase (EAL) catalyzes the conversion of ethanolamine to acetaldehyde and ammonia. As is the case for all AdoCbl-dependent isomerases, the catalytic cycle of EAL is initiated by homolytic cleavage of the cofactor's Co-C bond, producing Cocobalamin (CoCbl) and an adenosyl radical that serves to abstract a hydrogen atom from the substrate. Remarkably, in the presence of substrate, the rate of Co-C bond homolysis of enzyme-bound AdoCbl is increased by 12 orders of magnitude.
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Biophys J
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Department of Physics, Emory University, Atlanta, Georgia. Electronic address:
We address the contribution of select classes of solvent-coupled configurational fluctuations to the complex choreography involved in configurational and chemical steps in an enzyme by comparing native and nonnative reactions conducted at different protein internal sites. The low temperature, first-order kinetics of covalent bond rearrangement of the cryotrapped substrate radical in coenzyme B-dependent ethanolamine ammonia-lyase (EAL) from Salmonella enterica display a kink, or increase in slope, of the Arrhenius plot with decreasing temperature. The event is associated with quenching of a select class of reaction-actuating collective fluctuations in the protein hydration layer.
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Chembiochem
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Department of Bioscience and Biotechnology, Graduate School of Natural Science and Technology, Okayama University, Tsushima-naka, Okayama 700-8530, Japan.
Adenosylcobalamin (AdoCbl), or coenzyme B , is a naturally occurring organometallic compound that serves as a cofactor for enzymes that catalyze intramolecular group-transfer reactions and ribonucleotide reduction in a wide variety of organisms from bacteria to animals. AdoCbl-dependent enzymes are radical enzymes that generate an adenosyl radical by homolysis of the coenzyme's cobalt-carbon (Co-C) bond for catalysis. How do the enzymes activate and cleave the Co-C bond to form the adenosyl radical? How do the enzymes utilize the high reactivity of the adenosyl radical for catalysis by suppressing undesirable side reactions? Our recent structural studies, which aimed to solve these problems with diol dehydratase and ethanolamine ammonia-lyase, established the crucial importance of the steric strain of the Co-C bond and conformational stabilization of the adenosyl radical for coenzyme B catalysis.
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Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, Faculty of Life Sciences and Medicine, Xi'an No.3 Hospital, The Affiliated Hospital of Northwest University, Northwest University, Xi'an, Shaanxi, 710069, PR China; Department of Endocrinology, Xi'an No.3 Hospital, The Affiliated Hospital of Northwest University, Northwest University, Xi'an, Shaanxi, 710018, PR China; Xi'an Key Laboratory of Cardiovascular and Cerebrovascular Diseases, Xi'an No.3 Hospital, The Affiliated Hospital of Northwest University, Northwest University, Xi'an, Shaanxi, 710018, PR China. Electronic address:
Article Synopsis
- Excessive free fatty acids (FFAs) contribute to insulin resistance (IR) in the liver, with a focus on the enzyme ethanolamine-phosphate phospho-lyase (ETNPPL), which is highly expressed in hepatic tissue.
- The study used cell models to demonstrate that ETNPPL levels rise in PA-induced IR and that silencing ETNPPL reduces IR effects, while its overexpression promotes IR and reactive oxygen species (ROS) generation.
- Targeting ETNPPL, especially using compounds like quercetin, shows potential in treating PA-induced IR, highlighting a possible therapeutic pathway for managing Type 2 diabetes.
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