Glycine dehydrogenase (decarboxylating)
Encyclopedia
Glycine dehydrogenase [decarboxylating], mitochondrial also known as glycine cleavage system P protein or glycine decarboxylase is an enzyme
that in humans is encoded by the GLDC gene
.
that catalyzes
the following chemical reaction
:
Thus, the two substrates
of this enzyme are glycine
and H-protein-lipoyllysine, whereas its two products
are H-protein-S-aminomethyldihydrolipoyllysine and CO2
.
This enzyme belongs to the family of oxidoreductase
s, specifically those acting on the CH-NH2 group of donors with a disulfide as acceptor. This enzyme participates in glycine, serine and threonine metabolism. It employs one cofactor
, pyridoxal phosphate.
in eukaryotes. The glycine cleavage system catalyzes the degradation of glycine. The P protein binds the alpha-amino group of glycine through its pyridoxal phosphate cofactor. Carbon dioxide is released and the remaining methylamine moiety is then transferred to the lipoamide cofactor of the H protein.
Degradation of glycine is brought about by the glycine cleavage system, which is composed of four mitochondrial protein components: P protein (a pyridoxal phosphate-dependent glycine decarboxylase), H protein (a lipoic acid-containing protein), T protein (a tetrahydrofolate-requiring enzyme), and L protein (a lipoamide dehydrogenase).
may be due to a defect in any one of these enzymes.
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 in humans is encoded by the GLDC gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
.
Reaction
Glycine dehydrogenase (decarboxylating) is an enzymeEnzyme
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 following 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...
:
- glycine + H-protein-lipoyllysine
H-protein-S-aminomethyldihydrolipoyllysine + CO2
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 glycine
Glycine
Glycine is an organic compound with the formula NH2CH2COOH. Having a hydrogen substituent as its 'side chain', glycine is the smallest of the 20 amino acids commonly found in proteins. Its codons are GGU, GGC, GGA, GGG cf. the genetic code.Glycine is a colourless, sweet-tasting crystalline solid...
and H-protein-lipoyllysine, 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 H-protein-S-aminomethyldihydrolipoyllysine and CO2
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
.
This enzyme belongs to the family of oxidoreductase
Oxidoreductase
In biochemistry, an oxidoreductase is an enzyme that catalyzes the transfer of electrons from one molecule to another...
s, specifically those acting on the CH-NH2 group of donors with a disulfide as acceptor. This enzyme participates in glycine, serine and threonine metabolism. It employs one cofactor
Cofactor (biochemistry)
A cofactor is a non-protein chemical compound that is bound to a protein and is required for the protein's biological activity. These proteins are commonly enzymes, and cofactors can be considered "helper molecules" that assist in biochemical transformations....
, pyridoxal phosphate.
Function
Glycine decarboxylase is a P-protein of the glycine cleavage systemGlycine cleavage system
The glycine cleavage system is also known as the glycine decarboxylase complex or GCS. The system is a series of enzymes that are triggered in response to high concentrations of the amino acid glycine. The glycine cleavage system is composed of four proteins: the T-protein, P-protein, L-protein,...
in eukaryotes. The glycine cleavage system catalyzes the degradation of glycine. The P protein binds the alpha-amino group of glycine through its pyridoxal phosphate cofactor. Carbon dioxide is released and the remaining methylamine moiety is then transferred to the lipoamide cofactor of the H protein.
Degradation of glycine is brought about by the glycine cleavage system, which is composed of four mitochondrial protein components: P protein (a pyridoxal phosphate-dependent glycine decarboxylase), H protein (a lipoic acid-containing protein), T protein (a tetrahydrofolate-requiring enzyme), and L protein (a lipoamide dehydrogenase).
Clinical significance
Glycine encephalopathyD-Glyceric acidemia
D-Glyceric Acidemia is an inherited disease, in the category of inborn errors of metabolism. It is caused by a mutation in the gene GLYCTK, which encodes the for the enzyme glycerate kinase.-Pathophysiology:...
may be due to a defect in any one of these enzymes.