三种螺旋藻及其蛋白质、多糖和脂类结合硒的研究

STUDY ON THE ACCUMULATION OF SELENIUM AND ITS BINDING TO THE PROTEINS, POLYSACCHARIDES AND LIPIDS FROM SPIRULINA MAXIMA, S.PLATENSIS AND S. SUBSALSA

于1992年9月—1995年1月将极大、钝顶、盐泽等三种螺旋藻在加4—100mg／L硒浓度的培养基内培养，研究藻细胞及其蛋白质、多糖和脂类结合硒的量，探讨硒的结合机理。结果表明，极大螺旋藻累积的硒随外加硒的浓度而增加，但累积系数接近平均值2．184；在同样的硒浓度（8mg／L）条件下，盐泽螺旋藻对硒的累积远大于极大和钝顶两种螺旋藻的，高达696．968×10－6；极大螺旋藻中蛋白质和脂类结合的硒分别占藻细胞含硒量的14．63％和16．05％，两者均高于其它两种藻中相对应的量；三种藻细胞多糖结合硒的能力均很弱，但胞外多糖结合硒的能力较强。根据实验结果推测，螺旋藻累积硒的机理一方面是大分子化合物的吸附作用，另一方面是通过生化过程使硒与蛋白质和脂类结合形成大分子化合物。

The present experiments were carried out from September 1992 toJanuary 1995, and the algal species were provided by Laboratory of Algal Researeh,Department of Biological Science and Technology, Nanjing University. The culture ofa blue-green alga Spirulina maxima in the Zarrouk's media with various contents ofsoditun selenite, i. e. 4, 8, 12, 16, 20, 40, 60, 80 and 100 mg/ L selenium, showstha selenium ascumulated by thes alga increases with added selenite, bu theaccumulation ratio is close to a mean value of 2.184 (Tab. 1). According to thisobservation, the culture condition of 8 mg/ L selenium was chosen to compare theaccumulation of selenitnn in S. maxima, S platensis and S subsalsa, to study themechanisms of mis accumulation. In the medium containing 8 mg/L selenium, S.subsalsa accumulated 696.968μg selenium per gram dry weight (Tab.2), which was 72and 5.7 times as much as S.matoa and S.platensis, respectively. After preliminarypurification, the crude isolated proteins of these algae were sepaatd on Sephadexthloo column chromatography into Parts A, B and C (Fig. 1), and the lipids on silicagel column into poar and neutra lipids. Selenium bound to protoins and lipids in Smadria accounted for 14.63% and 16.05% (Tab. 3), respectively, of the total seleniumaccumulthed, much higher than those of S.platensis and S.subsalsa, althongh theabsolute contents of selenium accumulated by S.maxima were lower than S.platensisand S.subsalsa (Tab.2). Half of selenium bound to proteins was in Part A(Tab.3),which was almost chlorophyll-bound proteins (Fig.2), while that bound to polar lipidaccounted for two thirds of its tota content in lipids (Tab. 3). The extheellularpolysaccharides were sepotd into frashons Ⅰand Ⅱ on DEAE-Sephadex A-25column chromatography, while the endocellular ones also into fmehons Ⅰand Ⅱ withthe exception of these in S.platensis consisting of only one fraction. The fact thatselenium bound tO the extrdeellular polysaccharides was much higher than tha to theendocellular ones (Fig. 3) indicares that the extracellular polysascharides are very easyto form coordination compounds with selenium, while the endocellular polysaccharidescould not easily do this way. From the above results the mechanisms of seleniumaccumulation by these algae are deduced to be physical absorphon by macromolecules,e. g. the peptidoglycan of the algal cell walls, and biochemical formation ofseleno-macromolecullar compounds with the proteins and lipids, such as thereplasement of sulfur by selenium in peptides. S.platensis and S.subsalsaaccumulated selenium mainly by the former mechanism, and S.maxima accumulared itdominantly by the latter one.