Cyanophycin
Encyclopedia
Cyanophycin, or multi-L-arginyl-poly (L-aspartic acid), is a non-protein
, non-ribosomally produced amino acid
polymer
composed of an aspartic acid
backbone and arginine
side groups.
Cyanophycin was first detected in 1887 by an Italian scientist (Borzi, 1887) and can be found in most cyanobacteria and a few heterotrophic bacteria such as Acinetobacter
sp.. Cyanophycin is largely insoluble under physiological conditions and is accumulated in the form of granules in the cytoplasm
during phosphate or sulfur starvation, generally in the early and mid-stationary phase. It is used as a nitrogen- and possibly carbon-storage compound and also serves as a dynamic buffer for fixed nitrogen in cyanobacterial heterocysts. Nitrogen and carbon are mobilized from cyanophycin by intracellular cyanophycinase in the form of aspartate-arginine dipeptide
s.
Cyanophycin is synthesized from arginine and aspartate in an ATP
-dependent reaction catalyzed
by a single enzyme
, cyanophycin synthetase . Cyanophycin is of potential interest to biotechnology
as a source of polyaspartic acid. Due to its unusual polyamphoteric character, cyanophycin is soluble in water under acidic (0.1 M HCl) and alkali conditions. Heterologous expression of cyanophycin synthetase allows production of cyanophycin in a number of biotechnologically relevant bacteria such as Escherichia coli
and Corynebacterium glutamicum .
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
, non-ribosomally produced amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...
composed of an aspartic acid
Aspartic acid
Aspartic acid is an α-amino acid with the chemical formula HOOCCHCH2COOH. The carboxylate anion, salt, or ester of aspartic acid is known as aspartate. The L-isomer of aspartate is one of the 20 proteinogenic amino acids, i.e., the building blocks of proteins...
backbone and arginine
Arginine
Arginine is an α-amino acid. The L-form is one of the 20 most common natural amino acids. At the level of molecular genetics, in the structure of the messenger ribonucleic acid mRNA, CGU, CGC, CGA, CGG, AGA, and AGG, are the triplets of nucleotide bases or codons that codify for arginine during...
side groups.
Cyanophycin was first detected in 1887 by an Italian scientist (Borzi, 1887) and can be found in most cyanobacteria and a few heterotrophic bacteria such as Acinetobacter
Acinetobacter
Acinetobacter [asz−in−ée−toe–back−ter] is a genus of Gram-negative bacteria belonging to the Gammaproteobacteria. Acinetobacter species are non-motile and oxidase-negative, and occur in pairs under magnification....
sp.. Cyanophycin is largely insoluble under physiological conditions and is accumulated in the form of granules in the cytoplasm
Cytoplasm
The cytoplasm is a small gel-like substance residing between the cell membrane holding all the cell's internal sub-structures , except for the nucleus. All the contents of the cells of prokaryote organisms are contained within the cytoplasm...
during phosphate or sulfur starvation, generally in the early and mid-stationary phase. It is used as a nitrogen- and possibly carbon-storage compound and also serves as a dynamic buffer for fixed nitrogen in cyanobacterial heterocysts. Nitrogen and carbon are mobilized from cyanophycin by intracellular cyanophycinase in the form of aspartate-arginine dipeptide
Dipeptide
A dipeptide is a molecule consisting of two amino acids joined by a single peptide bond.Dipeptides are produced from polypeptides by the action of the hydrolase enzyme dipeptidyl peptidase. Dietary proteins are digested to dipeptides and amino acids, and the dipeptides are absorbed more rapidly...
s.
Cyanophycin is synthesized from arginine and aspartate in an ATP
Adenosine triphosphate
Adenosine-5'-triphosphate is a multifunctional nucleoside triphosphate used in cells as a coenzyme. It is often called the "molecular unit of currency" of intracellular energy transfer. ATP transports chemical energy within cells for metabolism...
-dependent reaction catalyzed
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....
by a single enzyme
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...
, cyanophycin synthetase . Cyanophycin is of potential interest to biotechnology
Biotechnology
Biotechnology is a field of applied biology that involves the use of living organisms and bioprocesses in engineering, technology, medicine and other fields requiring bioproducts. Biotechnology also utilizes these products for manufacturing purpose...
as a source of polyaspartic acid. Due to its unusual polyamphoteric character, cyanophycin is soluble in water under acidic (0.1 M HCl) and alkali conditions. Heterologous expression of cyanophycin synthetase allows production of cyanophycin in a number of biotechnologically relevant bacteria such as Escherichia coli
Escherichia coli
Escherichia coli is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms . Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls...
and Corynebacterium glutamicum .