Isolation, Purification and Properties of an R-Phycocyanin from the Phycobilisomes of a Marine Red Macroalga Polysiphonia urceolata

Abstract

Phycobilisomes were prepared from a marine red macroalga Polysiphonia urceolata (P. urceolata) by sucrose step-gradient ultracentrifugation. From the prepared phycobilisomes, an R-phycocyanin was isolated by gel filtration on Sephadex G-150 and then purified by ion exchange chromatography on DEAE-Sepharose Fast Flow and native polyacrylamide gel electrophoresis (PAGE) performed in neutral buffer systems. The purified R-phycocyanins showed not only a homogeneous trimer of 136 kDa in gel filtration and a single band in native PAGE, but also exhibited one band at about pH 5.7 in native isoelectric focusing (IEF). By a gradient SDS-PAGE the purified R-phycocyanin was determined to contain one α subunit of 17.5 kDa (α 17.5) and two β subunits of 21.3 kDa and 22.6 kDa (β 21.3 and β 22.6). The analysis from denaturing isoelectric focusing and two-dimension PAGE demonstrated that α 17.5, β 21.3 and β 22.6 had their pIs of 6.4, 5.3 and 5.4, respectively. Furthermore, mass spectroscopy analysis of β 21.3 and β 22.6 by MALDI-TOF mass spectrometry demonstrated the two β subunits had differences in peptide mass fingerprinting. These results revealed that the prepared R-phycocyanins were composed of one α and two β subunits. and , which have a structural foundation to show their pIs too close for them to be definitely resolved by native IEF, are postulated to be the most possible trimeric forms of the R-phycocyanins prepared from the phycobilisomes of P. urceolata.

Nutraceutical properties of phycocyanin

“…Formerly, it was believed that PC was not light sensitive (Abeliovich & Shilo, Shanab et al (2012) 1972) but recent evidences indicate that it is light sensitive and must be kept in darkness (Benedetti et al, 2006;Wang et al, 2014). In fact, PC produces reactive oxygen species (ROS) under light conditions as it is described later.…”

“…This pigment is found in cyanobacteria and eukaryotic algae such as Rhodophyta and Cryptomonads (Glazer & Stryer, 1983). PC is classified into three types, C-PC (obtained from cyanobacteria), R-PC (obtained from red algae) and R-PCII (obtained from Synechococcus species) (Kuddus, Singh, Thomas, & Al-Hazimi, 2013;Wang et al, 2014). In this review, the general properties of the three types of PC are described.…”

“…The isoelectric point of PC varies between 4.1 and 6.4 depending on the algae source and methods employed for extraction and purification (Chen & Wong, 2008;Silveira et al, 2008;Wang et al, 2014); its extinction coefficient (E 1% 1 cm) at 620 nm is of 770,000 M −1 cm −1 (Benedetti et al, 2004). Formerly, it was believed that PC was not light sensitive (Abeliovich & Shilo, Shanab et al (2012) 1972) but recent evidences indicate that it is light sensitive and must be kept in darkness (Benedetti et al, 2006;Wang et al, 2014).…”

Identification and antioxidant activity of synthetic peptides from phycobiliproteins of Pyropia yezoensis

“…However, PC-β was not observed in the protein samples analyzed in the present study. PC in seaweed is usually a monomer with a molecular weight of 40 kDa, and is composed of an α-chain with a molecular weight of 18.5 kDa and β-chain with a molecular weight of 20.5 kDa, and two or three blue-colored phycocyanobilin molecules bind with one phycoerythrobilin molecule ( 35 , 36 ). PC in red algae is the R-type with an absorption band between 615 and 620 nm, however, certain types show an absorption band at 550 nm, caused by phycoerythrobilin ( 33 ).…”

“…In APC, a monomer with a molecular weight of 15.5 kDa forms a hexamer ( 35 , 36 ). APC is less abundant than PE or PC and, like PC, has a bond between phycocyanobilin and the protein.…”