Cyanophycin

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.

[1] 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.

Due to its unusual polyamphoteric character, cyanophycin is soluble in water under acidic (0.1 M HCl) and alkaline conditions.

The ability of lysine to partially replace the arginine side chain encouraged research of CGP variants with amino acids such as ornithine and citrulline.

[4] Wiefel, Bröker and Steinbüchel conducted an experiment demonstrating that citrulline-rich cyanophycin can be produced through the introduction of a citrulline-producing strain.