Related Experiment Video
Updated: Jul 5, 2026
08:59
Defining Substrate Specificities for Lipase and Phospholipase Candidates
Published on: November 23, 2016
Structural basis for natural lactonase and promiscuous phosphotriesterase activities
Mikael Elias1, Jérôme Dupuy, Luigia Merone
1Laboratoire de Cristallographie et Modélisation des Matériaux Minéraux et Biologiques, CNRS-Université Henri Poincaré, 54506 Nancy, France.
Journal of Molecular Biology
|May 20, 2008
Summary
Organophosphate-degrading enzymes are crucial for detoxification. Sulfolobus solfataricus phosphotriesterase (SsoPox) exhibits high lactonase activity, suggesting a novel biological function beyond organophosphate hydrolysis.
Area of Science:
- Biochemistry
- Enzymology
- Structural Biology
Background:
- Organophosphates are widely used insecticides and potent nerve agents.
- Organophosphate-degrading enzymes are vital for bioscavenging and decontamination.
- A hyperthermophilic phosphotriesterase, SsoPox, from Sulfolobus solfataricus, displays significant lactonase activity.
Purpose of the Study:
- To elucidate the three-dimensional structures of SsoPox.
- To investigate the structural basis for SsoPox's lactonase activity.
- To propose a refined catalytic mechanism for phosphotriesterases and lactonases.
Main Methods:
- X-ray crystallography to determine SsoPox structures (apo and ligand-bound).
- Site-directed mutagenesis to probe enzyme function.
- Biochemical assays to measure enzyme activity.
Main Results:
- Determined the 3D structures of SsoPox in apo and lactone-mimic bound states.
- Revealed an unexpected active site topology and a hydrophobic channel accommodating the lactone substrate.
- Provided evidence supporting lactonase activity as the primary function of SsoPox.
Conclusions:
- SsoPox possesses a unique structure enabling efficient lactone hydrolysis.
- The study refines the catalytic mechanisms of phosphotriesterases and lactonases.
- Enzyme promiscuity is a significant source for evolving new catalytic functions.
Related Concept Videos
01:25Inducible Operons: lac Operon
The lac operon in Escherichia coli is a model for understanding inducible gene regulation and metabolic flexibility. It integrates local control by lactose and global regulation through catabolite repression, enabling E. coli to preferentially metabolize glucose when available and switch to lactose utilization when glucose is scarce.Structure and Function of the lac OperonThe lac operon contains three structural genes: lacZ (β-galactosidase), lacY (lactose permease), and lacA (thiogalactoside...
01:19Allosteric 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,...
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,...
00:49Ligand 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...
02:40Ligand Binding Sites
Proteins are dynamic macromolecules that carry out a wide variety of essential processes; however, the activities of most proteins depend on their interactions with other molecules or ions, known as ligands.
Protein-ligand interactions are quite specific; even though numerous potential ligands surround a cellular protein at any given time, only a particular ligand can bind to that protein. Moreover, a ligand binds only to a dedicated area on the surface of the protein, known as the...
Protein-ligand interactions are quite specific; even though numerous potential ligands surround a cellular protein at any given time, only a particular ligand can bind to that protein. Moreover, a ligand binds only to a dedicated area on the surface of the protein, known as the...
02:09Operons
Prokaryotes can control gene expression through operons—DNA sequences consisting of regulatory elements and clustered, functionally related protein-coding genes. Operons use a single promoter sequence to initiate transcription of a gene cluster (i.e., a group of structural genes) into a single mRNA molecule. The terminator sequence ends transcription. An operator sequence, located between the promoter and structural genes, prohibits the operon’s transcriptional activity if bound by a repressor...
02:54Protein Kinases and Phosphatases
Proteins undergo chemical modifications that trigger changes in the charge, structure, and conformation of the proteins. Phosphorylation, acetylation, glycosylation, nitrosylation, ubiquitination, lipidation, methylation, and proteolysis are various protein modifications that regulate protein activity. Such modifications are usually enzyme-driven.
Protein kinases
Many proteins in the cell are regulated by phosphorylation, the addition of a phosphate group. A family of enzymes called kinases...
Protein kinases
Many proteins in the cell are regulated by phosphorylation, the addition of a phosphate group. A family of enzymes called kinases...