盐泽螺旋藻藻胆蛋白的分离和特性研究
PURIFICATION AND PROPERTIES OF PHYCOBILIPROTEIN OF SPIRULINA SUBSALSA VAR.
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摘要: 盐泽螺旋藻(Spirulina subsalsa)的水溶性色素粗提物经过硫酸铵沉淀和羟基磷灰石(HA)柱层析后可以分出两种藻胆蛋白,即藻蓝蛋白(c-PC)和别藻蓝蛋白(APC)。它们的纯度(指其在可见光部分的最大吸收与280nm处吸收之比)可分别达到7.27(c-PC)和6.55(APC)。而一般认可的纯度标准,PC为5,APC为6。纯化后的c-PC和APC在聚丙烯酰胺凝胶电泳(PAGE)中仅见一条色带,其最大吸收峰分别在620nm和650nm,其室温荧光发射峰分别为642nm和657nm。通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE),无论胶浓度在11.5%或是在7—15%的梯度中,c-PC均可分为α和β两个亚单位,而APC除α和β两个亚单位外,在7—15%梯度SDS-PAGE中还偶见一个14kD左右的无色多肽,它可能与APC结合较紧密,为藻胆体“核”亚结构的组分,类似于Glazer(198522报道的聚胞藻(Synechocystis)6701中的10kD多肽。盐泽螺旋藻的c-PC和APC的亚单位分子量分别为:c-PC-α,16.0kD;c-PC-β,19.5kD;APC-α,15.5kD;APC-β,18.0kD。依此推算该藻的c-PC和APC的最小分子量应为35.5kD和33.5kD。它与钝顶螺旋藻(Spirulina platensis)相比显得稍低,但又略高于其它几种蓝藻。经等电电泳法测定,其c-PC和APC的等电点分别在4.4和4.6,它与以往报道的一些蓝藻大抵相当。盐泽螺旋藻的藻胆蛋白占细胞干重的28.4%左右,可望成为人类优良的蛋白源。Abstract: Two types of phycobiliproteins, C-PC and APC, were separated just after crude phycobiliproteins from S. subsalsa var. were precipitated in 50% (NH4)SO4 and then loaded on a 1×4cm hydroxylapatite column.The C-PC with a purity of 7.27 (A 620/A 280) possesses absorption maximum at 620 nm and a room fluorescence emission at 642 nm, while the APC with a purity of 6.55 (A 650/A 280) have an absorption maximum at 650 nm and a room fluorescence emission at 657 nm.When the purified C-PC and APC were electrophoresed under non-denaturing PAGE condition, only one band was observed (data not shown). Under denaturation (by means of 11.5% SDS-polyacrylamide slab gels or 7—15% SDS polyacrylamide slab gels), C-PC yielded two coloured polypeptides with the molecular weights of 16.0 and 19.5 kD for its α and β subunits, respectively; whereas APC comprised two slightly coloured polypeptides of molecular weights of 15.5 and 18.0 kD for its α and β subunits, respectively. Sometimes APC had a colorless polypeptide band with a molecular weight of 14.0 kD which was probably a core component of phycobilisome as discussed by Glazer in 1985 for Synechocystis 6701. According to these data, the minimum molecular weights (C-PC, 35,500; APC, 33,500) of phycobiliproteins from S. subsalsa var. are smaller than those from S. plantensis. The amino acid composition and isoelectric points of C-PC and APC were also determined.The total content of phycobiliproteins was estimated at 28.4% of dry weight of S. subsalsa var. Thus it is higher than that of other blue-green algae.The above results show that Spirulina subsalsa var. is an ideal source for edible protein.