[1][2][3] It catalyses the following chemical reaction The enzyme is highly specific for the branched polypeptide cyanophycin.

Site directed mutagenesis experiments confirmed that the enzyme is a serine protease and suggested that Ser 132 is the primary catalytic residue.

Other key residues for specificity include Gln101, Asp172, Gln173, Arg178, Arg180 and Arg183 which form a conserved pocket adjacent to Ser 132.

[5] Cyanophycin is highly resistant to degradation by all conventional proteases, and the only enzyme known to be capable of hydrolyzing it is cyanophycinase.

Cyanophycin is a non-ribosomally synthesized peptidyl polymer that is used for nitrogen storage by cyanobacteria and other select eubacteria.