Cyanophycin granules

Some cyanobacteria possess cyanophycin, which is a copolymer of aspartic acid and arginine (Lawry and Simon, 1982). This copolymer is accumulated in the granules, and its localization in complexes with PolyP is not improbable. 

In this chapter, we focus on the synthesis of polyhydroxyalkanoic acids (PHA) and cyanophycin (cyanophycin granule polyperptide, CGP) and the key enzymes PHA synthase (PhaC) and cyanophycin synthetase (CphA), respectively. Both polymers are synthesized by template-independent processes. The issue of template dependency and template independency will be illustrated in more detail with polymers consisting of amino acids. 

The third mechanism is represented by nonmodular one-step peptide synthesis. Enzymes belonging to this group catalyze the biosynthesis of poly(amino acids). Naturally occurring poly(amino acids) comprise cyanophy-cin [multi-L-arginyl-poly-(L-aspartic acid) cyanophycin granule polypeptide, (CGP)], (poly-(e-lysine) (PL), and poly-(y-glutamate) (PGA). As a consequence of non-ribosomal biosynthesis these peptides reveal a polydisperse mass distribution. 

Simon, R.D. (1973) The effect of chloramphenicol on the production of cyanophycin granule polypeptide in the blue-green alga Anabaena cylindrica. Arch. Mikrobiol., 92,115-122. 

Simon, R.D. (1971) Cyanophycin granules from the blue-green alga Anahaena cylindrica a reserve material consisting of copolymers of aspartic acid and arginine. Proc. Natl. Acad. 

For large-scale recombinant production of bacterial polymers, non-polymer producing bacteria were exposed to biosynthesis pathways. Polymers such as PHA, CGP (cyanophycin granule peptide), HA (hyaluronic acid), and PGA [poly-y-glutamate] were produced by these methods [89, 85-96]. For example, recombinant E.coli [89] was fermented for the lai e-scale production of PHA [89]. In addition the PHB biosynthesis genes of Ralstonia eutropa were harbored in E.coli to produce poljmers such as PHA composed of (R)-S-hydroxybutyrate and (R)-3-hydroxyvalerate and/or (R)-3-hydroxyhexanoate which showed preferable properties for use in industrial applications [97-99, 85-96]. 

Cyanophycin granule polypeptide (CGP) is a microbial poly(amino acid) synthesized and sequestered as inclusion bodies by cyanobacteria [310] and other microorganisms [311]. CGP is composed of a poly(aspartic acid) (poly(Asp)) backbone chain with arginine (Arg) residues attached as pendant groups (Figure 2.41) [311]. 

No ultrastructural evidence exists so far for the occurrence of similar inclusions in other organisms, and as such it is not possible to identify material with the typical characteristics of cyanophycin from other sources. The granules made of cyanophycin vary in size and shape [313, 314] and occur in aU cyanobacterial groups unicellular and filamentous, nitrogen-fixing, and non-nitrogen-fbdng. Cyanophycin... 

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