Antioxidant Activity of Recombinant Allophycocyanin β-Subunit (Holo-apcB)
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Abstract:
In this study, a recombinant allophycocyanin β-subunit (holo-apcB) [Thermosynechococcus elongatus BP-1] was biosynthesized in recombinant Escherichia coli by using metabolic engineering technology. Holo-apcB was then isolated and purified using affinity chromatography. SDS-PAGE analysis showed that there was a band with a molecular weight close to 18.4 ku, which matched the theoretical molecular weight of holo-apcB. Spectrum analysis showed the maximum absorbance and maximum fluorescence emission of holo-apcB were at 615 nm and 640 nm, respectively. Thus, this subunit had the same molecular weight and spectroscopic properties as those of holo-apcB. At 55 ℃, the half-life of holo-apcB reached up to 31.9 h. Comparison of the antioxidant activity of holo-apcB with native allophycocyanin (APC) and apo-apcB showed that holo-apcB had the highest antioxidant activity. Moreover, the holo-apcB IC50 values for hydroxyl and peroxyl radical-scavenging activities were 224.9 μg/mL and 20.6 μg/mL, respectively, which were significantly lower than those for apo-apcB and native APC. Therefore, it was suggested that phycocyanobilin also has antioxidant functions.
