Komath S S, Bhanu K, Maiya B G, Swamy M J
School of Chemistry, University of Hyderabad, India.
Biosci Rep. 2000 Aug;20(4):265-76. doi: 10.1023/a:1026440907227.
Jacalin (Artocarpus integrifolia agglutinin) specifically recognizes the tumor-associated T-antigenic disaccharide structure, Gal beta13GalNAc. Porphyrins and their derivatives are currently used as photosensitizers in photodynamic therapy to treat malignant tumors. In this study, the interaction of several free base porphyrins and their metal derivatives with jacalin is investigated by absorption and fluorescence spectroscopy. Each lectin subunit was found to bind one porphyrin molecule and the association constants were estimated to be in the range of 2.4 x 10(3) M(-1) to 1.3 x 10(5) M(-1) at room temperature for the interaction of different porphyrins with jacalin. These values are in the same range as those obtained for the interaction of monosaccharides to jacalin. Both free lectin and lectin saturated with the specific saccharide were found to bind different porphyrins with comparable binding strength indicating that porphyrin binding takes place at a site different from the sugar binding site. Further, both anionic and cationic porphyrins were found to interact with the lectin with comparable affinity, clearly indicating that the charge on the porphyrin does not play any role in the binding process and that most likely the interaction is mediated by hydrophobic forces. These results suggest that jacalin and other lectins may potentially be useful for targeted delivery of porphyrins to tumor tissues in photodynamic therapy.
杰克豆凝集素（菠萝蜜凝集素）能特异性识别肿瘤相关的T抗原二糖结构，即β-半乳糖基-1,3-N-乙酰半乳糖胺。卟啉及其衍生物目前被用作光动力疗法中治疗恶性肿瘤的光敏剂。在本研究中，通过吸收光谱和荧光光谱研究了几种游离碱卟啉及其金属衍生物与杰克豆凝集素的相互作用。发现每个凝集素亚基结合一个卟啉分子，在室温下，不同卟啉与杰克豆凝集素相互作用的缔合常数估计在2.4×10³ M⁻¹至1.3×10⁵ M⁻¹范围内。这些值与单糖与杰克豆凝集素相互作用所获得的值在同一范围内。发现游离凝集素和被特定糖类饱和的凝集素以相当的结合强度结合不同的卟啉，这表明卟啉结合发生在与糖结合位点不同的位点。此外，发现阴离子和阳离子卟啉都以相当的亲和力与凝集素相互作用，这清楚地表明卟啉上的电荷在结合过程中不起任何作用，并且最有可能的是这种相互作用是由疏水作用力介导的。这些结果表明，杰克豆凝集素和其他凝集素可能在光动力疗法中用于将卟啉靶向递送至肿瘤组织。
