Open AccessBiosynthesis of the cyanobacterial reserve polymer multi‐L‐arginyl‐poly‐L‐aspartic acid (cyanophycin)
Author(s) -
Berg Holger,
Ziegler Karl,
Piotukh Kirill,
Baier Kerstin,
Lockau Wolfgang,
VolkmerEngert Rudolf
Publication year - 2000
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1046/j.1432-1327.2000.01622.x
Subject(s) - aspartic acid , amino acid , biochemistry , arginine , lysine , biosynthesis , enzyme , chemistry , stereochemistry , amino acid synthesis , glutamic acid
Biosynthesis of the cyanobacterial nitrogen reserve cyanophycin (multi‐ l ‐arginyl‐poly‐ l ‐aspartic acid) is catalysed by cyanophycin synthetase, an enzyme that consists of a single kind of polypeptide. Efficient synthesis of the polymer requires ATP, the constituent amino acids aspartic acid and arginine, and a primer like cyanophycin. Using synthetic peptide primers, the course of the biosynthetic reaction was studied. The following results were obtained: (a) sequence analysis suggests that cyanophycin synthetase has two ATP‐binding sites and hence probably two active sites; (b) the enzyme catalyses the formation of cyanophycin‐like polymers of 25–30 kDa apparent molecular mass in vitro; (c) primers are elongated at their C‐terminus; (d) the constituent amino acids are incorporated stepwise, in the order aspartic acid followed by arginine, into the growing polymer. A mechanism for the cyanophycin synthetase reaction is proposed; (e) the specificity of the enzyme for its amino‐acid substrates was also studied. Glutamic acid cannot replace aspartic acid as the acidic amino acid, whereas lysine can replace arginine but is incorporated into cyanophycin at a much lower rate.