Comparison of biological activities of human antithrombins with high-mannose or complex-type nonfucosylated N-linked oligosaccharides

• Published in: Glycobiology (Oxford) 2016-05, Vol.26 (5), p.482-492
• Main Authors: Yamada, Tsuyoshi, Kanda, Yutaka, Takayama, Makoto, Hashimoto, Akitoshi, Sugihara, Tsutomu, Satoh-Kubota, Ai, Suzuki-Takanami, Eri, Yano, Keiichi, Iida, Shigeru, Satoh, Mitsuo
• Format: Article
• Language: English
• Subjects: Antithrombin Proteins - chemistry; Antithrombin Proteins - metabolism; Glycosylation; Heparin - chemistry; Heparin - metabolism; Humans; Mannose - chemistry; Mannose - metabolism; Oligosaccharides - chemistry; Oligosaccharides - metabolism; ORIGINAL ARTICLES; Protein Binding
• ISSN: 0959-6658; 1460-2423
• DOI: 10.1093/glycob/cww001

The structure of the N-linked oligosaccharides attached to antithrombin (AT) has been shown to affect its anticoagulant activity and pharmacokinetics. Human AT has biantennary complex-type oligosaccharides with the unique feature of lacking a core fucose, which affects its biological activities by changing its heparin-binding affinity. In human plasma, AT circulates as a mixture of the α-form bearing four oligosaccharides and the β-form lacking an oligosaccharide at Asn135. However, it remains unclear how the immature high-mannose-type oligosaccharides produced by mammalian cells affect biological activities of AT. Here, we succeeded in directly comparing the activities between the high-mannose and complex types. Interestingly, although there were no substantial differences in thrombin inhibitory activity, the high-mannose type showed higher heparin-binding affinity. The anticoagulant activities were increased by heparin and correlated with the heparin-binding affinity, resulting in the strongest anticoagulant activity being displayed in the β-form with the high-mannose type. In pharmacokinetic profiling, the high-mannose type showed a much shorter plasma half-life than the complex type. The β-form was found to have a prolonged plasma half-life compared with the α-form for the high-mannose type; conversely, the α-form showed a longer half-life than the β-form for the complex-type. The present study highlights that AT physiological activities are strictly controlled not only by a core fucose at the reducing end but also by the high-mannose-type structures at the nonreducing end. The β-form with the immature high-mannose type appears to function as a more potent anticoagulant than the AT typically found in human plasma, once it emerges in the blood.