Protein-glutamate methylesterase
Encyclopedia
In enzymology, a protein-glutamate methylesterase is an enzyme
that catalyzes
the chemical reaction
Thus, the two substrates
of this enzyme are protein L-glutamate O5-methyl ester and H2O
, whereas its two products
are protein L-glutamate and methanol
.
This enzyme is a demethylase
, and more specifically it belongs to the family of hydrolase
s, specifically those acting on carboxylic ester
bonds. The systematic name of this enzyme class is protein-L-glutamate-O5-methyl-ester acylhydrolase. Other names in common use include chemotaxis-specific methylesterase, methyl-accepting chemotaxis protein methyl-esterase, CheB methylesterase, methylesterase CheB, protein methyl-esterase, protein carboxyl methylesterase, PME, protein methylesterase, and protein-L-glutamate-5-O-methyl-ester acylhydrolase. This enzyme participates in 3 metabolic pathways
: two-component system - general, bacterial chemotaxis - general, and bacterial chemotaxis - organism-specific.
CheB is part of a two-component signal transduction
system. These systems enable bacteria
to sense, respond, and adapt to a wide range of environments, stressors, and growth conditions. Two-component systems are composed of a sensor histidine
kinase
(HK) and its cognate response regulator (RR). The HK catalyses
its own autophosphorylation
followed by the transfer of the phosphoryl
group to the receiver domain on RR; phosphorylation
of the RR usually activates an attached output domain, in this case a methyltransferase domain.
CheB is involved in chemotaxis
. CheB methylesterase is responsible for removing the methyl group
from the gamma-glutamyl methyl ester residues in the methyl-accepting chemotaxis protein
s (MCP). CheB is regulated through phosphorylation by CheA
. The N-terminal region of the protein is similar to that of other regulatory components of sensory transduction systems.
have been solved for this class of enzymes, with PDB
accession codes and .
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
that catalyzes
Catalysis
Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....
the chemical reaction
Chemical reaction
A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...
- protein L-glutamate O5-methyl ester + H2O
protein L-glutamate + methanol
Thus, the two substrates
Substrate (biochemistry)
In biochemistry, a substrate is a molecule upon which an enzyme acts. Enzymes catalyze chemical reactions involving the substrate. In the case of a single substrate, the substrate binds with the enzyme active site, and an enzyme-substrate complex is formed. The substrate is transformed into one or...
of this enzyme are protein L-glutamate O5-methyl ester and H2O
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
, whereas its two products
Product (chemistry)
Product are formed during chemical reactions as reagents are consumed. Products have lower energy than the reagents and are produced during the reaction according to the second law of thermodynamics. The released energy comes from changes in chemical bonds between atoms in reagent molecules and...
are protein L-glutamate and methanol
Methanol
Methanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with the formula CH3OH . It is the simplest alcohol, and is a light, volatile, colorless, flammable liquid with a distinctive odor very similar to, but slightly sweeter than, ethanol...
.
This enzyme is a demethylase
Demethylase
Demethylases are enzymes that remove methyl groups from proteins and other substances. They are used in a variety of processes, such as in chemotaxis signal transduction.-Hydrolytic demethylation:A good example of a demethylase is the activated Demethylases are enzymes that remove methyl (CH3-)...
, and more specifically it belongs to the family of hydrolase
Hydrolase
In biochemistry, a hydrolase is an enzyme that catalyzes the hydrolysis of a chemical bond. For example, an enzyme that catalyzed the following reaction is a hydrolase:-Nomenclature:...
s, specifically those acting on carboxylic ester
Ester
Esters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH group is replaced by an -O-alkyl group, and most commonly from carboxylic acids and...
bonds. The systematic name of this enzyme class is protein-L-glutamate-O5-methyl-ester acylhydrolase. Other names in common use include chemotaxis-specific methylesterase, methyl-accepting chemotaxis protein methyl-esterase, CheB methylesterase, methylesterase CheB, protein methyl-esterase, protein carboxyl methylesterase, PME, protein methylesterase, and protein-L-glutamate-5-O-methyl-ester acylhydrolase. This enzyme participates in 3 metabolic pathways
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...
: two-component system - general, bacterial chemotaxis - general, and bacterial chemotaxis - organism-specific.
CheB is part of a two-component signal transduction
Signal transduction
Signal transduction occurs when an extracellular signaling molecule activates a cell surface receptor. In turn, this receptor alters intracellular molecules creating a response...
system. These systems enable bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
to sense, respond, and adapt to a wide range of environments, stressors, and growth conditions. Two-component systems are composed of a sensor histidine
Histidine
Histidine Histidine, an essential amino acid, has a positively charged imidazole functional group. It is one of the 22 proteinogenic amino acids. Its codons are CAU and CAC. Histidine was first isolated by German physician Albrecht Kossel in 1896. Histidine is an essential amino acid in humans...
kinase
Kinase
In chemistry and biochemistry, a kinase is a type of enzyme that transfers phosphate groups from high-energy donor molecules, such as ATP, to specific substrates, a process referred to as phosphorylation. Kinases are part of the larger family of phosphotransferases...
(HK) and its cognate response regulator (RR). The HK catalyses
Catalysis
Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....
its own autophosphorylation
Autophosphorylation
In biochemistry, autophosphorylation is the process in which a protein kinase attaches a phosphate group to itself. This usually lead to kinase activation or regulation, and phosphorylation of other kinase substrates....
followed by the transfer of the phosphoryl
Phosphate
A phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in...
group to the receiver domain on RR; phosphorylation
Phosphorylation
Phosphorylation is the addition of a phosphate group to a protein or other organic molecule. Phosphorylation activates or deactivates many protein enzymes....
of the RR usually activates an attached output domain, in this case a methyltransferase domain.
CheB is involved in chemotaxis
Chemotaxis
Chemotaxis is the phenomenon in which somatic cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment. This is important for bacteria to find food by swimming towards the highest concentration of food molecules,...
. CheB methylesterase is responsible for removing the methyl group
Methyl group
Methyl group is a functional group derived from methane, containing one carbon atom bonded to three hydrogen atoms —CH3. The group is often abbreviated Me. Such hydrocarbon groups occur in many organic compounds. The methyl group can be found in three forms: anion, cation and radical. The anion...
from the gamma-glutamyl methyl ester residues in the methyl-accepting chemotaxis protein
Methyl-accepting chemotaxis protein
Methyl-accepting chemotaxis protein is a transmembrane sensor protein of bacteria. Use of the MCP allows bacteria to detect concentrations of molecules in the extracellular matrix so that the bacteria may smooth swim or tumble accordingly...
s (MCP). CheB is regulated through phosphorylation by CheA
Chea
Chea , is a Chinese surname common in China and Cambodia. Chea is romanized from the Chaozhou or Taishanese dialects of Chinese...
. The N-terminal region of the protein is similar to that of other regulatory components of sensory transduction systems.
Structural studies
As of late 2007, two structuresTertiary structure
In biochemistry and molecular biology, the tertiary structure of a protein or any other macromolecule is its three-dimensional structure, as defined by the atomic coordinates.-Relationship to primary structure:...
have been solved for this class of enzymes, with PDB
Protein Data Bank
The Protein Data Bank is a repository for the 3-D structural data of large biological molecules, such as proteins and nucleic acids....
accession codes and .