Abstract

The red alga Kappaphycus striatus is economically important food species and extensively cultivated throughout most tropical parts of the world as a source of carrageenan. In this note, the primary structure of a new lectin KSL from this alga was elucidated by the rapid amplification method of complementary DNA (cDNA) ends, which consists of 267 amino acid residues distributed in four tandem-repeated domains of about 67 amino acids and sharing 43% of identity. The calculated molecular mass from the deduced sequence was consistent with that of natural KSL (27,826 Da) determined by electron spray ionization–mass spectrometry. The primary structure of KSL showed high similarity to those of the high mannose N-glycan specific lectins from marine red algae, ESA-2 from Eucheuma serra, EDA-2 from Eucheuma denticulatum, KSA-2 from Kappaphycus striatum, KAAs from Kappaphycus alvarezii and SfLs from Solieria filiformis, and from microorganisms, BOA from Burkholderia oklahomensis, MBHA from Myxococcus xanthus, OAA from Oscillatoria agardhii and PFL from Pseudomonas fluorescens. Furthermore, KSL showed anticancer effects against five carcinoma cell lines, HT29, Hela, MCF-7, SK-LU-1 and AGS, in a dose-dependent manner with the IC₅₀ values of 0.80–1.94 µM, whereas its inhibition activities on cancer cells were not detected in the presence of yeast mannan, an inhibitor against lectin KSL. The cultivated red alga K. striatus could also be a good source of functional lectin(s) for application as anticancer agents.

Graphic abstract

中文翻译：

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栽培红藻 Kappaphycus striatus 新凝集素的结构和抗癌活性

摘要

红藻Kappaphycus striatus是经济上重要的食物物种，在世界大部分热带地区广泛种植，作为角叉菜胶的来源。在本文中，通过互补 DNA (cDNA) 末端的快速扩增方法阐明了来自这种藻类的新凝集素 KSL 的一级结构，该末端由 267 个氨基酸残基组成，分布在约 67 个氨基酸的四个串联重复结构域中，并且共享 43% 的身份。从推导的序列计算的分子量与通过电子喷雾电离质谱法测定的天然 KSL (27,826 Da) 一致。KSL 的一级结构与来自海洋红藻的高甘露糖 N-聚糖特异性凝集素、来自Eucheuma serra的 ESA-2 具有高度相似性, EDA-2 来自Eucheuma denticulatum , KSA-2 来自Kappaphycus striatum , KAAs 来自Kappaphycus alvarezii和 SfLs 来自Solieria filiformis和微生物, 来自Burkholderia oklahomensis的 BOA , MBHA 来自Myxococcus xanthus , OAA 来自Oscillatoria agardhii和 PFL 来自荧光假单胞菌。此外，KSL 对五种癌细胞系 HT29、Hela、MCF-7、SK-LU-1 和 AGS 显示出抗癌作用，IC _{50呈剂量依赖性}值 0.80–1.94 µM，而在酵母甘露聚糖（一种凝集素 KSL 抑制剂）存在下未检测到其对癌细胞的抑制活性。培养的红藻K. striatus也可能是用作抗癌剂的功能凝集素的良好来源。

图形摘要