STRUCTURAL STUDY ON ARABINOGALACTAN-PROTEINS FROM PICEA-ABIES L. KARST

Two homogeneous arabinogalactan-proteins (AGPs) have been purified fro m spruce (Picea abies L. Karst) callus cells by ion-exchange and gel-p ermeation chromatography, followed by enzymic treatment. The apparent molecular masses of these highly glycosylated proteoglycans AGP-1 and AGP-2 were 43 and 19 kDa, respectively. Both macromolecules contained predominantly terminal alpha-L-arabinofuranosyl residues, terminal, 3- , 6-, and 3,6-linked beta-D-galactopyranosyl residues, and terminal be ta-D-glucopyranosyluronic acid residues. The presence of a pyruvate su bstituent on O-4,6 of some of the 3-linked beta-D-galactopyranosyl res idues was proved for both AGPs. The protein moiety was rich in hydroxy proline, serine, threonine, and alanine. Reductive alkaline degradatio n of the AGPs indicated that serine and threonine were not involved in the carbohydrate-protein linkage. While sharing general structural si milarity, these endoplasmic AGPs were distinguishable by composition, size, and shape of the macromolecules. (C) 1998 Elsevier Science Ltd. All rights reserved.