Characterization of the Hydrolysis Kinetics of Fucosylated Glycosaminoglycan in Mild Acid and Structures of the Resulting Oligosaccharides
Xixi Liu | Zhexian Zhang | Hui Mao | Pin Wang | Zhichuang Zuo | Li Gao | Xiang Shi | Ronghua Yin | Na Gao | Jinhua Zhao
Mild acid hydrolysis is a common method for the structure analysis of fucosylated glycosaminoglycan (FG). In this work, the effects of acid hydrolysis on the structure of FG from <i>S. variegatus</i> (SvFG) and the reaction characteristic were systemically studied. The degree of defucosylation (DF) and molecular weights (Mw) of partial fucosylated glycosaminoglycans (pFs) were monitored by <sup>1</sup>H NMR and size-exclusion chromatography, respectively. The kinetic plots of DF, degree of desulfation (DS) from fucose branches, and degree of hydrolysis (DH) of the backbone are exponentially increased with time, indicating that acid hydrolysis of SvFG followed a first-order kinetics. The kinetic rate constants <i>k<sub>D</sub></i><sub>F</sub>, <i>k<sub>D</sub></i><sub>S</sub>, and <i>k<sub>D</sub></i><sub>H</sub> were determined to be 0.0223 h<sup>-1</sup>, 0.0041 h<sup>-1</sup>, and 0.0005 h<sup>-1</sup>, respectively. The structure of the released sulfated fucose branches (FucS) from SvFG and HfFG (FG from <i>H. fuscopunctata</i>) was characterized by 1D/2D NMR spectroscopy, suggesting the presence of six types of fucose: α/β Fuc2S4S, Fuc3S4S, Fuc3S, Fuc4S, Fuc2S, and Fuc. The Fuc3S4S was more susceptible to acid than Fuc2S4S, and that the sulfate ester in position of O-2 and O-3 than in O-4 of fucose. The structure characteristic of pF18 indicated the cleavage of backbone glycosidic bonds. The APTT prolonged activity reduced with the decrease of the DF and Mw of the pFs, and became insignificant when its DF was 87% with Mw of 3.5 kDa.
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