Biosynthesis of fluorescent allophycocyanin α‐subunits by autocatalysis in Escherichia coli

APC (allophycocyanin) is widely used for fluorescence tagging and may be a promising antioxidant agent for use within the food and pharmaceutical industries. Chromophore attachment to apo‐ApcA (apo‐APC α‐subunit without chromophore) can be autocatalysed both in vitro and in vivo . In the present study, a plasmid containing genes of apo‐ApcA and chromophore synthetases [HO1 (ferredoxin‐dependent haem oxygenase) and PcyA (phycocyanobilin:ferredoxin oxidoreductase)] was constructed and expressed in Escherichia coli . The results show that holo‐ApcA (APC α‐subunit with chromophore) can be synthesized by autocatalysis in E. coli . Recombinant holo‐ApcA showed the same spectral and fluorescent properties as PC (phycocyanin) and could serve as a good substitute for native PC for fluorescent tagging. Moreover, recombinant ApcA can inhibit hydroxyl and peroxyl radicals more strongly than holo‐ApcA and native APC. The EC 50 values were 296.4±22.4 μg/ml against hydroxyl radicals and 38.5±2.6 μg/ml against peroxyl radicals.