Glutamate synthase (also known as Glutamine oxoglutarate aminotransferase) is an

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...

and frequently abbreviated as GOGAT. This enzyme manufactures

glutamate Glutamic acid (symbol Glu or E; the ionic form is known as glutamate) is an α-amino acid that is used by almost all living beings in the biosynthesis of proteins. It is a non-essential nutrient for humans, meaning that the human body can synt ...

from

glutamine Glutamine (symbol Gln or Q) is an α-amino acid that is used in the biosynthesis of proteins. Its side chain is similar to that of glutamic acid, except the carboxylic acid group is replaced by an amide. It is classified as a charge-neutral ...

and α-ketoglutarate, and thus along with

glutamine synthetase Glutamine synthetase (GS) () is an enzyme that plays an essential role in the metabolism of nitrogen by catalyzing the condensation of glutamate and ammonia to form glutamine: Glutamate + ATP + NH3 → Glutamine + ADP + phosphate Glutam ...

(abbreviated GS) plays a central role in the regulation of

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

assimilation in photosynthetic eukaryotes and prokaryotes."Phylogenetic Relationships Among Glutamate Synthase (GOGAT) Enzymes" Eva Zadykowicz and Deborah L. Robertson; Department of Biology, Clark University, Worcester, MA"Practical Streptomyces Genetics" Keiser et al; John Innes Foundation, Norwich, England This is of great importance as primary productivity in many marine environments is regulated by the availability of inorganic nitrogen. The primary sources of inorganic nitrogen used by marine algae are

nitrate Nitrate is a polyatomic ion with the chemical formula . Salts containing this ion are called nitrates. Nitrates are common components of fertilizers and explosives. Almost all inorganic nitrates are soluble in water. An example of an insolu ...

and

ammonium The ammonium cation is a positively-charged polyatomic ion with the chemical formula or . It is formed by the protonation of ammonia (). Ammonium is also a general name for positively charged or protonated substituted amines and quaterna ...

. Both forms are ultimately incorporated into amino acids through the sequential reaction of glutamine synthetase (GS) and glutamate synthase (glutamine:2-oxoglutarate aminotransferase; GOGAT). GOGAT isoenzymes catalyze the transfer of the amido nitrogen of glutamine to 2-oxoglutarate using pyridine nucleotides (

NADH Nicotinamide adenine dinucleotide (NAD) is a coenzyme central to metabolism. Found in all living cells, NAD is called a dinucleotide because it consists of two nucleotides joined through their phosphate groups. One nucleotide contains an aden ...

NADPH Nicotinamide adenine dinucleotide phosphate, abbreviated NADP or, in older notation, TPN (triphosphopyridine nucleotide), is a cofactor used in anabolic reactions, such as the Calvin cycle and lipid and nucleic acid syntheses, which require NA ...

-dependent) or

ferredoxin Ferredoxins (from Latin ''ferrum'': iron + redox, often abbreviated "fd") are iron–sulfur proteins that mediate electron transfer in a range of metabolic reactions. The term "ferredoxin" was coined by D.C. Wharton of the DuPont Co. and applied t ...

(ferredoxin dependent) as reductants. They are called NADH-GOGAT and Fd-GOGAT respectively. In photosynthetic eukaryotes, GS and GOGAT isoenzymes are localized in the

cytosol The cytosol, also known as cytoplasmic matrix or groundplasm, is one of the liquids found inside cells ( intracellular fluid (ICF)). It is separated into compartments by membranes. For example, the mitochondrial matrix separates the mitochondri ...

and

chloroplast A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it i ...

. Fd-GOGAT is found strictly in

cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, bl ...

and photosynthetic eukaryotes, and the gene is located in the chloroplast of

rhodophytes Red algae, or Rhodophyta (, ; ), are one of the oldest groups of eukaryotic algae. The Rhodophyta also comprises one of the largest phyla of algae, containing over 7,000 currently recognized species with taxonomic revisions ongoing. The majority ...

and in the nucleus of vascular plants, but in both cases its product is active in the chloroplast. NADH-GOGAT is found in the nucleus of vascular plants, fungi, and diatoms, while NADPH-GOGAT is found in non-photosynthetic bacteria and

archaea Archaea ( ; singular archaeon ) is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaeba ...

References

{{DEFAULTSORT:Glutamine Oxoglutarate Aminotransferase Enzymes

See also

References