www.elsevier.nl/locate/carres Carbohydrate Research 333 (2001) 79 – 85 Structural features of arabinogalactan – proteins from the fruit of Lycium chinense Mill. Xiaoming Qin, a Ryo Yamauchi, a Koichi Aizawa, b Takahiro Inakuma, b Koji Kato a, * a The United Graduate School of Agricultural Science, Gifu Uniersity, Science of Biological Resources, 1 -1 Yanagido, Gifu 501 -1193, Japan b Research Institute, Kagome, Co., Ltd., Nishinasuno, Nasu, Tochigi 329 -2762, Japan Received 17 October 2000; accepted 15 March 2001 Abstract In addition to the other arabinogalactan – proteins (AGPs) (Cp-1-C and -D) already reported, two kinds of AGP (Cp-2-B and Hp-2-C) were obtained from the fruit of Lycium chinense Mill. The ratio of arabinose to galactose was 1:1 in both samples, and the carbohydrate was linked O-glycosidically to serine in Cp-2-B, and to both serine and threonine residues of the protein in Hp-2-C. The weight-average molecular weight was 71,000 for Cp-2-B and 120,000 for Hp-2-C. Both samples also contained non-reducing terminal 3-O - and 4-O -substituted galacturonic acids. The ratio of 6-O -substituted galactose (linear part) and 3,6-di-O -substituted galactose (branching point) was almost unity in both samples, being obviously different from the case of Cp-1-C (predominant in the branching domain) and Cp-1-D (predominant in the linear domain). These results offer fresh insight into the grouping of the AGPs, based on the ratio of 6-O - and 3,6-di-O -substituted galactosyl residues. © 2001 Elsevier Science Ltd. All rights reserved. Keywords: Arabinogalactan – protein; Lycium chinense Mill. 1. Introduction We previously reported 1 that the polysac- charide extracted with cold water from the fruit of Lycium chinense Mill. was separated into three main fractions (Cp-1, -2, and -3) by DEAE-cellulose column chromatography (HCO 3 - form), and Cp-1 and Cp-2 were pre- sumed to be composed mainly of arabino- galactan – protein (AGP), and Cp-3 pectin. A hot-water soluble polysaccharide fraction ob- tained from the residue after cold-water ex- traction, was also separated into three main fractions (Hp-2, -3, and -4) by the same ion- exchange chromatography, and Hp-2 was also presumed to contain mainly AGP, and Hp-3 and -4 pectin. 1 In a subsequent paper, 2 Cp-1 was reported to be a mixture of four kinds of polysaccharide, two of which were tentatively identified as arabinoxylan (1:1 Ara:Xyl, Cp-1- A) and arabinan (Cp-1-B), and the others (Cp-1-C and -D) were clarified as being AGP. Here we report characterization of the AGPs (Cp-2-B from Cp-2 and Hp-2-C from Hp-2), and offer a fresh insight into a grouping of the AGP (type II) through the discussion that includes Cp-1-C and -D, which were reported previously. 2 2. Experimental Materials.—A cold-water-soluble poly- saccharide from the fruit was fractionated as * Corresponding author. Fax: +81-58-2932925. E -mail address: katokoji@cc.gifu-u.ac.jp (K. Kato). 0008-6215/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved. PII:S0008-6215(01)00118-5