魔芋球茎中的β-甘露聚糖酶

迄今研究高等植物的β-甘露聚糖酶主要是用贮藏甘露聚糖的种子为材料(Halmer等1975,Halmer和Bewley 1979,Reid等1977,McCleary 1983)。营养器官贮藏甘露聚糖的植物,仅存在于单子叶植物的少数科(Meier和Reid 1982)。魔芋球茎贮藏大量甘露聚糖,Sugiyama等(1973)和Shimahara等(1975)从萌发的球茎中部分纯化了β-甘露聚糖     

魔芋甘露聚糖化学结构的研究

研究了陕西花魔芋块茎中分离所得的魔芋甘露聚糖的化学结构与分子组成。经葡聚糖凝胶Ｇ－７５柱层析为一组均一性多糖,气相色谱检测由甘露糖,葡萄糖组成,其克分子比Ｍａｎ;Ｇｌｕ＝１．７８：１,平均分子量为１１×１０＾－５。     

魔芋葡甘聚糖的pH触发酶解

利用高效凝胶排阻色谱技术研究并实现了以溶液pH值为简易调节开关,对魔芋葡甘聚糖的酶解反应进行触发调控：结果表明：pH为4时底物分子量不发生变化,而当pH调至7时,酶解被触发进行,底物分子量随之快速下降。分析表明：酶在pH变化过程中发生部分复性的可能原因是pH由7调至4的过程中发生沉淀的酶分子维持了天然构象,当pH反调回7时重新溶解,并对KGM进行剪切。     

甘露聚糖结合蛋白基因突变引起的免疫缺陷

甘露聚糖结合蛋白基因突变引起的免疫缺陷陈政良（第一军医大学免疫学教研室,广州５１０５１５）关键词甘露聚糖结合蛋白基因突变免疫缺陷甘露聚糖结合蛋白（ＭＢＰ）是一种血清Ｃ型凝集素。其肽链包括Ｎ末端区、含Ｇｌｙ－Ｘ－Ｙ重复顺序的胶原样区（ｃｏｌａｇｅｎ－ｌ...     

魔芋葡甘露低聚糖的酶法制备工艺的初步研究

利用β-甘露聚糖酶产品水解魔芋胶制备魔芋葡甘露低聚糖的工艺条件。在加样顺序、pH、酶添加量、时间、温度等单因素试验的基础上,进一步通过正交试验确定的最佳工艺条件为:魔芋胶浓度10g/L,酶添加量为100U/g,pH5.5,45℃条件下,酶解时间1.5h。再利用酵母发酵去除可发酵性糖的方法,以获得最终产物为100%的魔芋葡甘露低聚糖。     

甘露聚糖结合蛋白选择性糖识别的分子机制

甘露聚糖结合蛋白选择性糖识别的分子机制陈政良（广州第一军医大学免疫学教研室,广州５１０５１５）关键词甘露聚糖结合蛋白,糖识别甘露聚糖结合蛋白（ｍａｎｎａｎ－ｂｉｎｄｉｎｇｐｒｏｔｅｉｎ,ＭＢＰ）是一种血浆蛋白,因被发现能选择性识别并结合酵母菌外壁上的...     

酵母甘露聚糖的结构确定与核磁共振谱的解析

本文采用多种化学方法与核磁共振(NMR)相结合确定甘露聚糖SP_1的结构。高碘酸盐氧化和甲基化衍生物的色-质联机分析(G.C.-M.S.)表明SP_1含有M-~1,-~2 M-~1,和-~6 M-~1*四种糖残基。部分酸水解和乙酰解证明SP_1的主链是1→6连接,侧链是1→2连接;其中长侧链有两个残基,短侧链只有一个残基。SP_1的~1H谱在H-1区出现四个较强和一个较弱的α型氢信号,~(13)C谱在C-1区出现三个较强的峰。它们的分布与化学方法所确定的结构基本一致。     

Resistant starch reduces colonic and urinary p-cresol in rats fed a tyrosine-supplemented diet,whereas konjac mannan does not

The effect of resistant starch (RS) and konjac mannan (KM) to maintain and improve the large intestinal environment was compared. Wistar SPF rats were fed the following diets for 4 weeks: negative control diet (C diet), tyrosine-supplemented positive control diet (T diet), and luminacoid supplemented diets containing either high-molecular konjac mannan A (KMAT diet), low-molecular konjac mannan B (KMBT diet), high-amylose cornstarch (HAST diet), or heat-moisture-treated starch (HMTST diet). The luminacoid-fed group had an increased content of short-chain fatty acids in the cecum. HAS caused a significant decrease in p-cresol content in the cecum, whereas KM did not. Urinary p-cresol was reduced in the HAST group compared with the T group, but not the KM fed groups. Deterioration in the large intestinal environment was only improved completely in the HAST and HMTST groups, suggesting that RS is considerably more effective than KM in maintaining the large intestinal environment.     

Starch biosynthesis: experiments on how starch granules grow in vivo

Four varieties of starch granules from potato, wheat, maize, and rice were fractionated into homogeneous 10-μm-sized ranges. The size with the largest amount of granules was reacted with ADP-[¹⁴C]Glc, washed, and peeled into 7−9 layers, using a controlled peeling process, involving 90:10 volume proportions of Me₂SO-H₂O at 10 °C. All of the starches showed biosynthesis of starch throughout the granules. Starch synthase activities were determined for each of the layers. Three of the starches had a relatively large amount of synthase activity in the second layer, with only a small amount in the first layer. Potato starch had the largest amount of activity in the first layer. Starch synthase activity was found to alternate between higher and lower activities throughout all of the varieties of granules, showing that the synthesis was not uniform and also was not exclusively occurring at the surface of the starch granules, which had previously been hypothesized. From these results and our previous studies on the mechanism of starch chain elongation by the addition of d-glucose to the reducing end of a growing chain that is covalently attached to the active site of starch synthase, a hypothesis is proposed for how starch granules grow in vivo.     

Determination of hydrophobicity of dry-heated wheat starch granules using sucrose fatty acid esters (SFAE)

Sucrose fatty acid esters (SFAE) were adsorbed onto dry-heated (120?°C for 10, 20, 40, 60, and 120?min) wheat starch granules and extracted with ethyl ether in a Soxhlet apparatus without gelatinization of the starch granules. The amount of sucrose in the extracted SFAE was determined by the phenol sulfate method. A gradual increase of the sucrose from 159 to 712?μg, in SFAE per gram of starch, occurred with increasing dry-heating time and demonstrated the increased hydrophobicity of the starch granules. Increase of the SFAE was highly correlated (r?=?0.9816) to increase of the oil-binding capacity of the dry-heated wheat starch granules. Non-waxy rice, waxy rice, sweet potato, and potato starch granules also showed higher hydrophobicity after dry-heating by this method.     

不同光照强度下花魔芋（Amorphophallus konjac）与谢君魔芋（Amorphophallus xiei）光合特性及光保护机制研究

为探讨不同耐光性植物光合特性及光保护机制,本研究以耐高光的喜阴植物花魔芋（Amorphophallus konjac K.Coch）和典型的喜阴植物谢君魔芋（Amorphophallus xiei H.Li & Z.L.Dao）为材料,测定与分析在透光率为100%、15%及2%光照条件下两种魔芋的光合能力、抗氧化酶活性及抗氧化物和光合色素组分的含量。结果表明,花魔芋最大光合速率和气孔导度随着生长环境光照强度降低而显著降低（P<0.05）,谢君魔芋在透光率为15%时最大光合速率达最大值。大部分情况下,花魔芋的超氧化物歧化酶、抗坏血酸过氧化物酶、过氧化氢酶、谷胱甘肽还原酶活性比谢君魔芋高（P<0.05）,而谢君魔芋具有较高的过氧化物酶活性（P<0.05）。总的来看,在中高光照环境下两种植物的抗氧化酶活性较高（P<0.05）。在透光率15%时,花魔芋谷胱甘肽和抗坏血酸显著比谢君魔芋高（P<0.05）。谢君魔芋的光合色素含量在透光率为15%时最高（P<0.05）;相应地,花魔芋的光合色素含量在透光率为2%时含量最低（P<0.05）;在不同光照强度下花魔芋光合色素含量基本上显著高于谢君魔芋（P<0.01）。本研究结果暗示,喜阴植物花魔芋耐受高光可能源于相对较高的光合作用能力和有效的光保护机制。     

禾谷类作物淀粉合酶

淀粉合酶是禾谷类作物淀粉合成所必需的一类酶.根据淀粉合酶家族成员的氨基酸序列的相似性,分别介绍了一个颗粒性淀粉合酶亚家族和四个可溶淀粉合酶亚家族的组成、基因结构和表达特点,并从转录、转录后和翻译后水平上对这些基因的表达调控做了概述.     

The phenotype of soluble starch synthase IV defective mutants of Arabidopsis thaliana suggests a novel function of elongation enzymes in the control of starch granule formation

All plants and green algae synthesize starch through the action of the same five classes of elongation enzymes: the starch synthases. Arabidopsis mutants defective for the synthesis of the soluble starch synthase IV (SSIV) type of elongation enzyme have now been characterized. The mutant plants displayed a severe growth defect but nonetheless accumulated near to normal levels of polysaccharide storage. Detailed structural analysis has failed to yield any change in starch granule structure. However, the number of granules per plastid has dramatically decreased leading to a large increase in their size. These results, which distinguish the SSIV mutants from all other mutants reported to date, suggest a specific function of this enzyme class in the control of granule numbers. We speculate therefore that SSIV could be selectively involved in the priming of starch granule formation.     

小麦花后弱光引起籽粒淀粉的粒度分布及组分含量的变化

在籽粒灌浆阶段(花后1～30 d)对小麦进行光强为自然光照45%的弱光处理,研究了小麦籽粒淀粉粒度分布和组分含量的变化.结果表明,小麦籽粒淀粉粒体积分布呈双峰曲线,峰值分别在5.1～6.1 μm和20.7～24.9 μm,两峰值间的低谷出现在9.9 μm左右.表面积分布和数目分布分别表现为双峰和单峰曲线.小麦花后弱光显著降低2.8～9.9 μm淀粉粒体积百分比,增加22.8～42.8 μm淀粉粒体积百分比.同时花后弱光显著降低<0.8 μm和2.8～9.8 μm淀粉粒表面积百分比,增加0.8～2.8 μm和>9.9 μm淀粉粒表面积百分比.可见灌浆期弱光显著降低籽粒B型(＜9.9 μm)淀粉粒体积和表面积百分比,而A型(＞9.9 μm)淀粉粒比例相对增加.与A型淀粉粒相比,B型淀粉粒对弱光的反映更敏感.小麦弱光处理籽粒淀粉及其组分含量显著低于对照,但其直/支比较对照高.相关分析表明,籽粒直/支比与2.8～9.9 μm淀粉粒体积百分比呈显著负相关,而与22.8～42.8 μm淀粉粒体积百分比呈显著正相关.花后不同阶段弱光显著增加A型淀粉粒体积百分比、降低B型淀粉粒体积百分比,其中灌浆中、后期弱光影响程度较前期大.表明,弱光条件下小麦籽粒淀粉合成底物优先供应淀粉粒的生长,而非形成更多的淀粉粒.     

Electron paramagnetic resonance study of water distribution in starch granules

An electron paramagnetic resonance (EPR) study was performed for potato and wheat starch containing Cu2+ ions as a paramagnetic probe. Distribution of water in the starch granules as well as the interactions between the copper and starch matrix of different crystalline structures were determined. EPR spectra of the native starches consisted of two different centers of Cu2+. One of them, giving at 293 and 77 K an EPR signal of axial symmetry with a well-resolved hyperfine structure (HFS), was assigned to the Cu2+ -starch complex in which Cu2+ ions strongly interacted with oxygen atoms of the starch matrix. Another Cu2+ species, exhibiting an isotropic signal at 293 K and an axial signal with resolved HFS at 77 K, was attributed to a [Cu(H2O)6]2+ complex freely rotating at room temperature and immobilized at low temperatures. Interaction of Cu2+ with the starch matrix and the relative number of the particular copper species depended on the crystallographic type of starch. Dehydration at 393 K resulted in elimination of the rotating complex signal and decrease of the total intensity of the EPR spectrum caused by clustering of the Cu2+ ions. Freezing at 77 K and thawing led to restoring of the spectrum intensity and reappearing of the signal of the [Cu(H2O)6]2+ complex. This effect, related to liberation of water molecules from the granule semicrystalline growth rings on freezing/thawing, was especially visible for wheat starch, indicating differences in the water retention ability of starch granules of different crystallographic structure.     

魔芋组织培养与细胞工程

近几年来,魔芋组织培养研究进展较快,其细胞工程领域也取得了一定的研究成果。现对魔芋组织培养过程中外植体取材、愈伤组织诱导与分化的激素应用进行了概述,重点介绍了魔芋离体形态建成的几种模式及其调控机制的研究新进展。有关魔芋种质资源离体保存和突变体的筛选的研究工作已经展开,其遗传转化体系也逐渐完善,外源基因如抗病基因、抗除草剂基因等现已转化成功。最后还对魔芋今后的研究方向进行了讨论,指出了目前存在的主要问题并提出了相应的对策。