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Arabinogalactan-proteins from cell suspension cultures of Araucaria angustifolia

Maurer, Juliana Bello Baron, Bacic, Antony, Pereira-Netto, Adaucto Bellarmino, Donatti, Lucelia, Zawadzki-Baggio, Selma Faria, Pettolino, Filomena Angela
Phytochemistry 2010 v.71 no.11-12 pp. 1400-1409
Araucaria angustifolia, endangered species, cell suspension culture, culture media, plant growth substances, arabinogalactans, plant proteins, chemical precipitation, chemical structure, monosaccharides, methylation, amino acid sequences, amino acid composition, binding sites, antibodies
Arabinogalactan-proteins (AGPs), found in the culture medium of suspension cells of Araucaria angustifolia grown in plant growth regulator-free and plant growth regulator-containing BM media, BM0 and BM2, respectively, were evaluated quantitatively and qualitatively. The concentrated extracellular fractions (CEFs), obtained from suspension cell cultures grown for 20 days in BM0 and BM2 media yielded two fractions, CEF-0 and CEF-2, respectively. CEF-0 and CEF-2 was submitted to selective precipitation using the β-glucosyl Yariv reagent (β-GlcY) to isolate AGPs for structural characterization; this yielded fractions designated CEF-0YPF and CEF-2YPF, respectively. The monosaccharide composition analysis established that samples were composed of Rha, Ara, Gal and uronic acid in a molar ratio 3:37:55:5 (CEF-0YPF) and 1:37:58:4 (CEF-2YPF), although trace amounts (<0.5 mol%) of Xyl were also found. Methylation analysis of CEF-YPF fractions showed similar results for both CEF-0YPF and CEF-2YPF, with non-reducing terminal units of Araf, Arap, Galp, Rhap and Xylp, as well as 3-O-substituted and 5-O-substituted Araf units and 3-O-substituted, 6-O-substituted and 3,6-di-O-susbtituted Galp units. The amino acid composition analysis established Ser, Ala, and Hyp as major amino acids in both samples. In conclusion, this investigation has shown that CEF-0YPF and CEF-2YPF contain macromolecules having typical AGP characteristics, including a Hyp/Ala/Ser-rich protein moiety, a (1 to 3) and/or (1 to 6) linked β-d-galactopyranosyl main chain substituted by Gal, Ara, Rha and Xyl residues, and binding affinity for β-GlcY and monoclonal anti-AGP antibodies.