Isolation and characterization of a Ca2+ -binding polysaccharide associated with coccoliths of Emiliania huxleyi (Lohmann) Kamptner.
Isolation and characterization of a Ca2+ -binding polysaccharide associated with coccoliths of Emiliania huxleyi (Lohmann) Kamptner.
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与 Emiliania huxleyi (Lohmann) Kamptner 球石相关的 Ca2 结合多糖的分离和表征。
DOI：
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发表时间：
1976
期刊：
影响因子：
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通讯作者：
P. Westbroek
中科院分区：
文献类型：
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作者：
E. Jong;L. Bosch;P. Westbroek
C-occolithophoridae是一组主要是单细胞的藻类，具有包含钙化板的细胞壁，称为球石。来自Emilania huxleyi（Lohmann）Kamptner种的球孢子含有水溶性酸性多糖。在本文中，我们描述了分离和多糖的一些特性，特别是其钙离子结合能力。研究了球石藻的大规模培养，并建立了分离球石藻的新方法。从球孢子获得的多糖含有两种类型的单硼酸基团，总量为1.8 μ mol/mg多糖。一类是由弱酸性基团组成的糖醛酸。强酸基团的性质仍有待确定。各组之间的比例为1：0.8。用~（45）Ca ~（2+）研究表明，该多糖具有与Ca ~（2+）结合的能力。平衡透析显示，0.92 +/- 0.05 mumol/mg多糖中可结合的Ca 2+的最大量。流速透析实验强烈建议存在两个类的Ca 2+结合位点不同的亲和力Ca 2+。发现高亲和力位点（对Ca 2+的解离常数Kd：2.2 +/- 1.0 × 10（-5）M）的存在量（0.38 +/- 0.04 μ mol/mg多糖）约等于上述强酸单价基团（0.8 μ mol/mg多糖）。低亲和力位点（对Ca 2+的Kd：-11 +/-39 X 10（-5）M）估计为0.74 +/-0.11 mumol/mg多糖。虽然这个数字可以确定不太准确，它表明，糖醛酸（1.0 μ mol/mg多糖）是相同的低亲和力网站。如凝胶过滤所示，在Na+和Mg 2+过量100倍时发生Ca 2+的优先结合。100倍过量的Sr ~（2+）在很大程度上抑制了Ca ~（2+）的结合，而在等摩尔量的La ~（3+）存在下没有Ca ~（2+）结合。用流速透析法测定了Na+、Mg ~（2+）、Sr ~（2+）和La ~（3+）在Ca ~（2+）存在下的高亲合位点的解离常数。它们证实了凝胶过滤发现的结合偏好顺序。从E. hyxleyi（约1000岁）。的可能作用的多糖作为一个异质基质中的颗石形成进行了讨论。
C-occolithophoridae, a group of mostly unicellular algae, possess a cell wall containing calcified plates, called coccoliths. The coccoliths from the species Emilania huxleyi (Lohmann) Kamptner contain a water-soluble acid polysaccharide. In this paper we describe the isolation and some characteristic properties of the polysaccharide, in particular its Ca2+ -binding capacity. A large-scale cultivation of the Coccolithophoridae was worked out and a new procedure for isolating coccoliths was developed. The polysaccharide obtained from the coccoliths contained two types of monobasic acid groups in a total amount of 1.8 mumol/mg polysaccharide. One type consisted of weakly acid groups which were identified as uronic acids. The nature of the stronger acid groups remains to be established. The ratio between the respective groups was 1:0.8. Studies with 45Ca2+ demonstrated that the isolated polysaccharide is capable of binding Ca2+. Equilibrium dialysis revealed that the maximum amount of Ca2+ which can be bound in 0.92 +/- 0.05 mumol/mg polysaccharide. Flow-rate dialysis experiments strongly suggested the presence of two classes of Ca2+ -binding sites differing in affinity for Ca2+. High-affinity sites (dissociation constant Kd for Ca2+ :2.2 +/- 1.0 X 10(-5) M) were found to be present in amounts (0.38 +/- 0.04 mumol/mg polysaccharide) approximately equivalent to the strongly acid monovalent groups mentioned above (0.8 mumol/mg polysaccharide). Low-affinity sites (Kd for Ca2+: -11 +/- 39 X 10(-5) M) were estimated at 0.74 +/- 0.11 mumol/mg polysaccharide. Although this figure could be determined less accurately, it is suggested that the uronic acids (1.0 mumol/mg polysaccharide) are identical to the low-affinity sites. Preferential binding of Ca2+ occurred in a 100-fold excess of Na+ and Mg2+ as was shown by gel filtration. A 100-fold excess of Sr2+ inhibited Ca2+ binding to a great extent while no Ca2+ was bound in the presence of an equimolar amount of La3+. The dissociation constants of the high-affinity sites for Na+, Mg2+, Sr2+ and La3+ (in the presence of Ca2+) were determined with the flow-rate dialysis technique. They confirm the order of binding preference found with gel filtration. A polysaccharide with similar properties could be isolated from subfossil coccoliths of E. hyxleyi (about 1000 years old). The possible role of the polysaccharide as a heterogeneous matrix in coccolith formation is discussed.