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Enzymes

Enzymes

Inside living organisms, enzymes act as catalysts for many biochemical reactions involved in cellular metabolism. The role of enzymes is to reduce the activation energies of biochemical reactions by forming complexes with its substrates. The lowering of activation energies favor an increase in the rates of biochemical reactions.
Enzyme deficiencies can often translate into life-threatening diseases. For example, a genetic abnormality resulting in the deficiency of the enzyme G6PD...

Allosteric Proteins-ATCase

Allosteric Proteins-ATCase

Binding sites linkages can regulate a protein's function. For example, enzyme activity is often regulated through a feedback mechanism where the end product of the biochemical process serves as an inhibitor.
Aspartate transcarbamoylase (ATCase) is a cytosolic enzyme that catalyzes the condensation of L-aspartate and carbamoyl phosphate to N-carbamoyl-L-aspartate. This reaction is the first step in pyrimidine biosynthesis. UTP and CTP, the end products of the pyrimidine synthesis pathway,...

Enzyme Inhibition

Enzyme Inhibition

Inhibitors are molecules that reduce enzyme activity by binding to the enzyme. In a normally functioning cell, enzymes are regulated by a variety of inhibitors. Drugs and other toxins can also inhibit enzymes. Some inhibitors bind to the enzyme’s active site, while others inhibit enzymatic activity by binding to other sites on the protein structure.

ATP Synthase: Mechanism

ATP Synthase: Mechanism

In animals, the mitochondrial F1F0 ATP synthase is the key protein that synthesizes ATP molecules through a complex catalytic mechanism. While the nuclear genome encodes the majority of ATP synthase subunits, the mitochondrial genome encodes some of the enzyme's most critical components. The formation of this multi-subunit enzyme is a complex multi-step process regulated at the level of transcription, translation, and assembly. Defects in one or more of these steps can result in decreased ATP...

ATP Synthase: Structure

ATP Synthase: Structure

ATP synthase or ATPase is among the most conserved proteins found in bacteria, mammals, and plants. This enzyme can catalyze a forward reaction in response to the electrochemical gradient, producing ATP from ADP and inorganic phosphate. ATP synthase can also work in a reverse direction by hydrolyzing ATP and generating an electrochemical gradient. Different forms of ATP synthases have evolved special features to meet the specific demands of the cell. Based on their specific feature, ATP...

Ligand Binding and Linkage

Ligand Binding and Linkage

Allosteric proteins have more than one ligand binding site; the binding of a ligand to any of these sites influences the binding of ligands to the other sites. When a protein is allosteric, its binding sites are called coupled or linked. In the case of enzymes, the site that binds to the substrate is known as the active site and the other site is known as the regulatory site. When a ligand binds to the regulatory site, this leads to conformational changes in the protein that can influence the...

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Related Experiment Video

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Modeling an Enzyme Active Site using Molecular Visualization Freeware

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Published on: December 25, 2021

The structure/function relationship of a dual-substrate (betaalpha)8-isomerase.

Helena Wright¹, Lianet Noda-García, Adrián Ochoa-Leyva

¹Department of Biological Sciences, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK.

Biochemical and Biophysical Research Communications

|October 31, 2007

Summary

Researchers determined the structure of phosphoribosyl isomerase A (PriA), crucial for histidine and tryptophan biosynthesis. This study reveals new molecular interactions and identifies key residues for enzyme function and conformational changes.

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Area of Science:

Biochemistry
Structural Biology
Enzymology

Background:

Phosphoribosyl isomerase A (PriA) is essential for both histidine and tryptophan biosynthesis pathways.
Understanding PriA's structure is key to elucidating its catalytic mechanisms and regulatory functions.

Purpose of the Study:

To determine the high-resolution structure of Streptomyces coelicolor PriA.
To identify the molecular basis for substrate recognition, catalysis, and conformational flexibility in PriA.

Main Methods:

X-ray crystallography was used to solve two structures of PriA at 1.8Å resolution.
Ligand-docking simulations were employed to predict functional residues.
Site-directed mutagenesis and functional assays were performed for validation.

Main Results:

The first complete structure of a closed conformer of PriA was obtained, revealing novel molecular interactions.
Key residues, including Arg19, Ser81, Asp11, Asp130, Thr166, and Asp171, were identified for substrate binding, catalysis, and conformational changes.
Mutagenesis and functional analyses confirmed the roles of these identified residues.

Conclusions:

This study provides the first detailed structure-function relationship for this (betaalpha)8-isomerase.
The findings offer insights into the catalytic mechanism and conformational dynamics of PriA, essential for amino acid biosynthesis.