User:Princessosma/Cyanophycin

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. It can also be abbreviated as CGP (cyanophycin granule polypeptide).

Cyanophycin was first detected in 1887 by the Italian botanist Antonino Borzì 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 dipeptides.

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 alkaline conditions. Heterologous expression of cyanophycin synthetase allows production of cyanophycin in a number of biotechnologically relevant bacteria such as Escherichia coli and Corynebacterium glutamicum.

Since insoluble forms of CGP are easily purified, most studies have overlooked the synthesis of CPG that is soluble at a neutral pH. To compare the two, insoluble CGP can be solubilized by only weak acids while soluble CGP can be separated with the process of precipitation by using acetone or ethanol. In 2014, an experiment by Steinbüchel and Wiefel determined that the amount of lysine residue can regulate the solubility of cyanophycin, with higher levels of lysine negatively correlating to the temperature needed to make the polymer soluble with aqueous solvents. It was concluded that insoluble and soluble CGP are not distinct polymers, since they originate from the same polymer mixture, but are instead classified as mixes of cyanophycin mixtures with varying concentrations of lysine residues.


 * 1) ^ Jump up to:a b c Wiefel, Lars; Steinbüchel, Alexander (2014-02-01). "Solubility Behavior of Cyanophycin Depending on Lysine Content". Applied and Environmental Microbiology. 80 (3): 1091–1096. doi:10.1128/AEM.03159-13. ISSN 0099-2240. PMC 3911199. PMID 24271185.