The enzyme, characterized from the cyanobacterium Microchaete diplosiphon, catalyses the attachment of the phycobilin chromophore (3E)-phycoerythrobilin (PEB) to cysteine 48 and 59 of the beta subunits of the phycobiliprotein C-phycoerythrin. The enzyme first ligates the A ring of PEB to cysteine-48, followed by the attachment of the D ring to cysteine-59. The numbering used here corresponds to the enzyme from Microchaete diplosiphon, and could vary slightly in other organisms. The reaction requires the presence of the chaperone-like protein CpeZ.
