Incorporation of haem into phycocyanobilin in levulinic acid treated Cyanidium caldarium.

Cells of the red alga Cyanidium caldarium were preincubated with 5 mmol 1(-1) levulinic acid (LA) and subsequently incubated with (14)C-labelled haem (5.67 Bq nmol(-1)). Phycocyanin was isolated. The specific radio-activity of its chromophore phycocyanobilin (PCB) was determined after cleavage and purification by thin layer chromatography. The percentage of PCB formed from labelled haem within 0.5 h was considerably higher in LA treated cells than in non-treated controls. This difference disappeared after prolonged incubation (16.5 h) with haem. The results are interpreted as possible incorporation of haem into preexisting apoprotein.