Phycocyanobilin is a blue phycobilin, i.e., a tetrapyrrole chromophore found in cyanobacteria and in the chloroplasts of red algae, glaucophytes, and some cryptomonads.

Phycocyanobilin is present only in the phycobiliproteins allophycocyanin and phycocyanin, of which it is the terminal acceptor of energy.

This PCB-HCA complex benefits the structure of HSA, increasing the thermal stability of HSA, as well as increasing its ability to prevent against proteolytic activity of other proteins.

[3] Four molecules of PBG are polymerized into a linear tetrapyrrole by Porphobilinogen deaminase.

Literature circa 1989 includes phytochromobilin as an intermediate in this final conversion.