Features of the biotechnologically relevant polyamide family “cyanophycins” and their biosynthesis in prokaryotes and eukaryotes

Abstract

Cyanophycin, inclusions in cyanobacteria discovered by the Italian scientist Borzi in 1887, were characterized as a polyamide consisting of aspartic acid and arginine. Its synthesis in cyanobacteria was analyzed regarding growth conditions, responsible gene product, requirements, polymer structure and properties. Heterologous expression of diverse cyanophycin synthetases (CphA) in Escherichia coli enabled further enzyme characterization. Cyanophycin is a polyamide with variable composition and physiochemical properties dependent on host and cultivation conditions in contrast to the extracellular polyamides poly-γ-glutamic acid and poly-ε-l-lysine. Furthermore, recombinant prokaryotes and transgenic eukaryotes, including plants expressing different cphA genes, were characterized as suitable for production of insoluble cyanophycin regarding higher yields and modified composition for other requirements and applications. In addition, cyanophycin was characterized as a source for the synthesis of polyaspartic acid or N-containing bulk chemicals and dipeptides upon chemical treatment or degradation by cyanophycinases, respectively. Moreover, water-soluble cyanophycin derivatives with altered amino acid composition were isolated from transgenic plants, yeasts and recombinant bacteria. Thereby, the range of dipeptides could be extended by biological processes and by chemical modification, thus increasing the range of applications for cyanophycin and its dipeptides, including agriculture, food supplementations, medical and cosmetic purposes, synthesis of the polyacrylate substitute poly(aspartic acid) and other applications.

The marine bacterium Phaeobacter inhibens secures external ammonium by rapid buildup of intracellular nitrogen stocks

“…The broad distribution of assimilated nitrogen into diverse cellular monomers and polymers reveals an intuitive nitrogen storage strategy in P. inhibens DSM 17395. Most cyanobacteria as well as some heterotrophic bacteria respond to surplus nitrogen supply by specifically boosting the biosynthesis of arginine, as major building block for the nitrogen-rich storage polymer cyanophycin (multi-L-arginyl-poly-L-aspartate) generated by cyanophycin synthetase (Frommeyer, Wiefel and Steinbüchel 2016). Lacking genes for the latter, P. inhibens DSM 17395 cannot synthesize cyanophycin.…”

A Novel Mechanism, Linked to Cell Density, Largely Controls Cell Division in Synechocystis

“…nutrients and light; Kim et al, 2011;Lea-Smith et al, 2014;Burnap, 2015;Touloupakis et al, 2015;van Alphen and Hellingwerf, 2015). Understanding of the factors controlling the limitation of Synechocystis growth would facilitate the use of this strain as a cell factory (Yu et al, 2013) for the production of biomass (Joseph et al, 2014), pigments (Sekar and Chandramohan, 2008), secondary metabolite natural products (Frommeyer et al, 2016), biofuel (Dexter and Fu, 2009;Baebprasert et al, 2011;Liu et al, 2011), and other high-value compounds.…”

Enzymatic Modification of Soluble Cyanophycin Using the Type II Peptidyl Arginine Deiminase from Oryctolagus cuniculus

“…After the first demonstration of a chemical modification of CGP by Frommeyer et al, this experimental study now shows that an enzymatic modification of the polymer is also possible . A partial modification of arginine side chains of the intact polymer as well as of the dipeptides could be detected after reaction with purified PADI; these modifications were absent in control experiments.…”

“…Therefore, the enzymatic modification of CGP was the next logical step. Currently, the only enzymes known to modify CGP are cyanophycinases found in several strains, such as species of Anabaena and Synechocystis . However, these enzymes do not modify the side chains, but cleave CGP into dipeptides.…”