Keywords: glycoprotein, complex type glycan, high mannose type glycan, N-glycan, erythropoietinin vitro folding protocol successfully generated a folded glycoprotein2-5). We also studied semi-synthesis method by means of E. coli expression system. A long peptide of nonglycosylated part in a target glycoprotein was prepared in E. coli and then chemical activations of its C-terminal or N-terminal was performed for peptide-glycopeptide couling6). Recently, we further developed semisynthesis method by means of glycosyl aspragine thioacid. This thioacid functional group serves to couple the N and C terminal peptides at the glycosyl asparagine site and this route gave glycoproteins within 5-6 chemical steps from glycosyl asparagine thioacid7). These methodologies successfully generated a series of glycoproteins varying glycosylation positions and numbers.Using homogeneous glycoproteins synthesized, we have studied how glycans regulate the glycoprotein quality control (GQC) system in the endoplasmic reticulum (ER) and bioactivity of cytokines. Special LectureAsparagine linked oligosaccharides (N-glycan) of protein play important roles in many biological events. In order to evaluate the function of N-glycans depending on glycosylation positions and glycosylation number, we have synthesized homogeneous glycoproteins. This presentation will introduce our synthesis and evaluation of N-glycans functions.For the study of N-glycan functions, we prepared homogeneous biantennary disialyl N-glycan from egg yolk over gram scale1) and then converted it into diverse symmetric or asymmetric N-glycans by the sequential glycosidase digestions or glycosyltransferase reactions. Using these glycans, we synthesized fluoromethyloxycarbonyl (Fmoc)-Asn-oligosaccharide or its tert-butylcarbonyl (t-Boc) forms for solid phase peptide synthesis (SPPS). Glycopeptides and peptide thus prepared were then coupled by native chemical ligation to yield a full-length target glycosyl polypeptide. Subsequent Yasuhiro Kajihara graduated from the Faculty of Engineering, Kanagawa University in 1988 and then received his master degree from the same university in 1990 (Supervisor: Prof. Ken-ichi Sato). In 1993, He received Ph.D. from Tokyo Institute of Technology (Supervisor: Prof. Hironobu Hashimoto). He spent two years at the Life Science Research Laboratory of Japan Tobacco Inc. as a postdoctoral fellow. During this period he studied the synthesis of glycosyltransferase inhibitors and synthesis methods for sugar nucleotides. In 1995 he joined Yokohama City University as an assistant professor. He promoted to associate professor in 2001 and Full Professor in 2007. At YCU, he developed the synthesis methods for oligosaccharides as well as for glycoproteins. In 2009, he moved to the Department of Chemistry, Osaka University. Currently, he studies new synthesis methods of homogeneous glycoproteins for the elucidation of glycan functions. He received Japan Society of Carbohydrate Research Incentive Award (2002), Award for creative research of Japanese Chemical Society (2014), and 2020 Roy L. Whistler International Award in Carbohydrate Chemistry (International Carbohydrate Organization).22Yasuhiro KajiharaDepartment of Chemistry, Osaka University15:00-15:40N-glycans on proteins3
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