Studies on the Precise Chemical Synthesis of Human Glycoproteins

Abstract

Our research group demonstrated the semi-synthesis of complex-type biantennary sialyloligosaccharide-library by means of branch-specific glycosidase and several sialyltransferase reactions toward complex-type H 2 N-Asn-(biantennary compex-type sialyloligosaccharide)-COOH isolated from egg yolk at over a gram scale. This methodology yielded 35 kinds of homogeneous complex-type oligosaccharides. Using this oligosaccharide library, an efficient Boc solid phase peptide synthesis (SPPS) of acid labile sialylglycopeptide-α-thioester was demonstrated. Our research group showed that the sialoside in which the carboxylic acid is protected with a phenacyl group is stable under strong acidic conditions, and this critical finding enabled us to demonstrate the first Boc-SPPS for the synthesis of a sialylglycopeptide-α-thioester. Using both a synthetic method of sialylglycopeptide-α-thioester and native chemical ligation (NCL), our research group synthesized several glycoproteins such as chemokine MCP-3, three kinds of erythropoietin analogues, and interferon-ß. Our research group also demonstrated a unique synthesis that was an intentional synthesis of homogeneous misfolded glycoproteins bearing M9-high-mannose-type oligosaccharide. This unique synthetic misfolded-glycoprotein is useful for the purpose of uncovering the mechanism of molecular recognition in glycoprotein quality control (GQC) in the endoplasmic reticulum (ER). This account discusses the function of the oligosaccharides of glycoproteins based on our research findings.

Recent advances in chemical synthesis of protein <italic>N</italic>-linked glycans

“…糖链结构所修饰 [1] . 不同的聚糖结构修饰影响糖蛋白 的生物功能, 如具有不同分支、含有或不含唾液酸的 复杂型糖链修饰的β-干扰素具有不同程度的抗癌活 性 [9] ; 多分支复杂型糖链对于维持糖蛋白促红细胞生 成素(erythropoietin, EPO)空间结构的稳定性发挥重要 作用, 且唾液酸N-糖链的数目直接影响其体内生物活 性 [10,11] ; 再如肝分泌糖蛋白(liver-secreted glycoproteins)的岩藻糖基化与肝癌的发生、发展密切相关 [12] . 由于氮连接聚糖巨大的结构多样性和复杂性, 研 究氮连接聚糖在各种生物过程中的分子基础和生物功 能面临极大的困难和挑战 [5] , 也对发展更加有效的工 具和方法提出了更高的要求.…”

Combination of Thiol‐Additive‐Free Native Chemical Ligation/Desulfurization and Intentional Replacement of Alanine with Cysteine

“…[1] Various synthetic methods have been reported, but native chemical ligation (NCL) is one of the most frequently used techniques. We synthesized stresscopin-related peptidea nd neuroendocrine regulatory peptide-2 (NERP-2) by this method.…”

“…[1] Various synthetic methods have been reported, but native chemical ligation (NCL) is one of the most frequently used techniques. [1] Various synthetic methods have been reported, but native chemical ligation (NCL) is one of the most frequently used techniques.…”

“…We confirmed that both conventional alkyl thioester and thioesterequivalent N-acyl-N'-methyl-benzimidazolinone (MeNbz) can be adopted as thioester components for thiol-additive-free NCL of multi-Cys-containing peptides.The total chemical synthesis of peptides/proteins has contributed much in the biological and medicinalf ields. [1] Various synthetic methods have been reported, but native chemical ligation (NCL) is one of the most frequently used techniques. [2] NCL involves the chemoselective reaction of ap eptide thioester with an N-terminal Cys-peptide in the presence of an excess of thiol additive, such as 4-mercaptophenylacetic acid (MPAA), [3] which acceleratest he ligation reaction.…”