Molecular properties of mycelial aggregate-specific lectin of Pleurotus cornucopiae

By cloning and sequencing cDNA, the primary structure of a mycelial aggregate-specific lectin of Pleurotus cornucopiae was determined. The amino acid sequence was novel and elucidated unique properties of this lectin: It was composed of 373 amino acids, 33 of which constitute a signal sequence. The sequence of the mature lectin consisted of two homologous regions having five glycosylation recognition signals and six cysteine residues. However, the distribution of these elements in the two regions was biased. Expression of cDNA in Escherichia coli and Pichia pastoris revealed the requirement of glycosylation to produce the functional lectin. Gel filtration followed by gel electrophoretic analyses of the purified lectin showed that the active component moved faster than the bulk of the protein, suggesting that the most active lectin formed an oligomer of subunits through disulfide bonds. From these observations, a model for the structure of the active form of this lectin is proposed. Southern hybridization using the cDNA as a probe revealed the presence of several genes. The lectin gene was composed of five exons and five introns.     

芸豆凝集素蛋白过敏原的检测及其脱敏食品加工工艺的研究进展

芸豆凝集素是芸豆中主要的过敏原蛋白之一,具有致敏剂量低、致死率高的特点,对芸豆消费安全具有重大隐患。如何快速、准确定量芸豆产品中的凝集素含量,并且在其食品加工中采用有效的脱敏食品加工工艺,是目前食品安全和卫生领域的研究热点。本文介绍了芸豆凝集素蛋白的致敏特点,重点列举、分析了芸豆凝集素的检测技术,主要包括红细胞凝集法、糖结合法、免疫法以及色谱和质谱检测方法,深入探讨了热处理、高压处理、辐照处理以及pH调控等食品加工工艺对芸豆凝集素潜在致敏性的影响,旨在为芸豆凝集素过敏防控及低敏芸豆类食品开发提供一定的理论参考。     

A garlic lectin exerted an antitumor activity and induced apoptosis in human tumor cells

Cytotoxic effects of a lectin prepared from garlic (Allium sativum-L) bulbs on human tumor cells were studied. The lectin strongly reduced the growth and DNA synthesis of human tumor cells in a time- and a dose-dependent manner. By contrast, a soybean lectin showed only a weak inhibitory effect on growth and DNA synthesis of tumor cells. Furthermore, the garlic lectin induced apoptosis in the cells at a low concentration. The antitumor activity of garlic lectin may provide a rational basis for its effectiveness observed in clinical applications.     

Thermal stability of black turtle soup bean (Phaseolus vulgaris) lectins

A method for determining the thermal stability of porcine thyroglobulin (PTG)-binding lectins in whole black turtle soup beans (Phaseolus vulgaris L) is described. The procedure utilises PTG-Sepharose affinity chromatography and the Folin-Ciocalteau protein assay. The majority of lectin activity in whole black turtle soup beans was destroyed by heating presoaked beans at 97.8°C for 10 min whereas unsoaked beans required 20 min of heat treatment at 97.8°C. Residual lectin activity was eliminated by thermally processing the presoaked and unsoaked beans for 25 and 50 min at 97.8°C, respectively. Thermal inactivation of the lectin in the whole seed is a biphasic, first-order reaction mechanism. Lectin-rat intestinal epithelial cell binding studies indicated the presence of a second lectin in the BTS albumin protein fraction. The lectin lacked an affinity for PTG and was inactivated by heating unsoaked whole beans for 50 min at 97.8°C.     

Mechanism of seed lectin tolerance by a major insect storage pest of Phaseolus vulgaris,acanthoscelides obtectus

The bean weevil Acanthoscelides obtectus (Say) is a major storage peat of Phaseolus vulgaris L (kidney, haricot bean). The seeds of P vulgaris contain high levels (up to 30 mg g^?1 DM) of lectin, which has been shown to be toxic towards larvae of the related bruchid storage pest of cowpea, Callosobruchus maculatus F. The lack of toxicity of this lectin towards larvae of A obtectus is demonstrated. Unlike the strong binding of lectin to the midgut epithelium observed in larvae of C maculatus, no binding of lectin molecules was found to occur in the gut epithelial cells of A obtectus. This observation provides the basis for a hypothesis explaining the lack of toxicity of P vulgaris lectin towards A obtectus. Assays of proteolytic activity in gut homogenates of C maculatus and A obtectus suggest that the difference in susceptibility of the two insects towards the toxic effects of the lectin is not due to differential inactivation by proteolysis. Besides its effects on larval development, the lectin has a further effect at pupation, causing disruption of adipose tissues in C maculatus but having no effect on A obtectus.     

A thermostable lectin from the rhizomes of Kaempferia parviflora

BACKGROUND: Kaempferia parviflora, or black galingale (Kra‐Chai‐Dam), belongs to the Zingiberaceae family and is used as both a food ingredient and a medicinal plant. There are diverse reports on the biological activities of compounds extracted from the plant, such as antimalarial, antifungal and an effective sexual‐enhancing role, but not on the lectins. RESULTS: A lectin was isolated from the rhizomes of Kaempferia parviflora using affinity chromatography on Concanavalin A followed by gel filtration chromatography on Sephacryl S‐100. The molecular weight of the purified lectin was about 41.7 kDa. This lectin showed haemagglutinating activity against erythrocytes from several sources, with the highest level being against those from rabbits. Moreover, the lectin was thermostable, with significant haemagglutinating activity detectable up to 75 °C. The results of trypsin digestion and liquid chromatography/tandem mass spectrometry analysis suggested that this protein could be a member of the lectin/endochitnase1 family. CONCLUSION: A lectin that showed thermotolerant haemagglutinating activity against erythrocytes from several sources was successfully purified from K. paviflora rhizomes. Peptide sequence analysis indicated that this lectin is similar to lectin/endochitinase 1 (Urtica dioica) or Hevein‐like protein (Hevea brasiliensis). Copyright © 2010 Society of Chemical Industry     

核桃凝集素的提取及其性质

以核桃仁为材料,对核桃凝集素的分离条件及其部分性质进行研究。结果表明：凝集活性值能准确反映凝集素的血凝效果;核仁经PBS缓冲液（pH 7.4）浸提24 h及质量分数70%硫酸铵分级沉淀,得到的核桃凝集素粗品能凝集人A、B、O、AB型血红细胞,且无血型专一性,其凝集活性不能被常见的单糖和寡糖抑制,但可被糖的衍生物所抑制;凝集活性在30～50 ℃基本不变,有较广泛的pH值作用范围（5.0～8.0）;供试的5 个核桃品种中,薄壳香粗提液的凝集活性最强,凝集活性值达到0.478。     

大豆凝集素的超声波辅助提取工艺优化及其性质

采用响应面法优化超声波辅助提取大豆凝集素的最佳工艺参数。在单因素试验的基础上,以超声时间、提取温度、提取时间、液料比为自变量,以凝集素提取得率为响应值,优化得到大豆凝集素的最佳提取工艺为：超声时间38 min、提取温度32 ℃、提取时间5.6 h、液料比10∶1（mL/g）。在此条件下得到的凝集素提取得率为9.82%。稳定性测定结果表明：大豆凝集素的最适pH值为7～8,在Ca2＋溶液中较稳定。D-乙酰葡萄糖胺和D-乙酰乳糖胺对大豆凝集素的凝集活力影响大,是大豆凝集素的专一性抑制糖。     

A MARANTHUS CRUENTUS LECTIN: PURIFICATION, STABILITY, AND SOME BIOCHEMICAL PROPERTIES

Amaranth lectin from Amaranthus cruentus seeds was isolated, purified and partially characterized. The purification method used was based on its ability to interact with fetuin. Effects of temperature, pH and buffers and concentration were determined by measurement of lectin hemagglutination activity. Amaranth lectin biological activity was best maintained at temperatures between 4 and 30°C and pH's above or below 5. It was possible to store amaranth lectin at 4°C in acetate buffers, pH 4.8, for prolonged periods and to concentrate it 10-fold by ultrafiltration with only 18% loss of activity. A subunit molecular weight of 32,500 daltons was determined by SDS-PAGE for amaranth lectin.     

Effect of Lectins on Salivary and Pancreatic Amylase Activities and tlhe Rate of Starch Digestion

Digestion of wheat starch (WS) and red kidney bean (RKB) starch by pancreatic (PA) and salivary (SA) amylase in the presence or absence of lectins was determined. Compared with WS, digestion of RKB starch by PA and SA was 70.0% and 66.6% lower, respectively. RKB lectin added to WS at the hemagglutinin activity level in RKB starch resulted in significantly decreased digestion with PA (63.9%) and SA (43.8%) as did heated RKB lectin with insignificant hemagglutinin activity (41.1% with PA, 35.8% with SA). Jack bean lectin (concan-avalin A) also resulted in reduced rate of starch digestibility. Kinetic analyses revealed noncompetitive inhibition by RKB lectins on both amylases. Results confirmed the role of lectin in reducing the rate of starch digestion and its possible health benefit.     

Effect of dietary sub-lethal doses of lima bean lectin on relative organ weights, pancreatic and intestinal trypsin (EC 3.4.21.4) and chymotrypsin (EC 3.4.21.1) in the rat

The dietary implications of feeding sub-lethal doses of extracted and purified lectin from lima bean were assessed in weanling rats using changes in relative organ weights, pancreatic and intestinal trypsin and chymotrypsin activities as the response indices. Liver weights decreased significantly (p less than 0.05) while the heart showed a slight but non-significant increase in response to dietary lectin levels. The kidneys, pancreas and spleen were not significantly affected by dietary lectin. Although the activities of the pancreatic enzymes tended, for the most part, to decrease with increasing dietary lectin, such decreases were not significant when compared with the control. Intestinal trypsin and chymotrypsin activities were significantly (p less than 0.05) decreased in the small intestine while the activity values in both the large intestine and caecum were relatively unaffected. Activities of both enzymes showed significant (p less than 0.05) negative quadratic relationship with dietary lectin levels in the small intestine as judged by the magnitude of the R2, coefficients of multiple determination, of 0.77 and 0.76 for trypsin and chymotrypsin respectively.     

THE LECTINS AND LECTIN-LIKE PROTEINS OF TEPARY BEANS (PHASEOLUS ACUTIFOLIUS) AND TEPARYCOMMON BEAN (PHASEOLUS VULGARIS) HYBRIDS

High levels of lectin activity were found in sixty cultivated and ten wild tepary (Phaseolus acutifolius) accessions. No lectin deficient varieties were observed and all examples studied contained both the phytohemagglutinin-E and L-like lectins previously described (Pusztai et al. 1987). There appeared to be no obvious differences between the wild and cultivated forms of the tepary lectins and all teparies studied contained lectin-like proteins in addition to the tepary lectins. One of the lectin related proteins (40 Kdalton subunit) was present in all teparies and may be comparable to arcelin, a lectin found in certain wild accessions of Phaselus vulgaris. All wild teparies contained a lectin related polypeptide of about 34 Kdaltons which appears to distinguish the wild teparies from the cultivated forms. Three tepary-common bean hybrids were examined and one hybrid was found to be expressing both tepary and common bean lectin genes.     

食品加工工艺对大豆内源基因降解变化规律的影响

本文以转基因大豆和非转基因大豆为试验材料，运用定性PCR技术分析了磨浆、煮浆、调配、均质、点浆、杀菌、喷雾干燥等豆腐、豆奶、豆粉三种豆制品中关键加工工艺对大豆内源基因lectin的影响，探讨了转基因大豆加工食品在不同加工过程中DNA降解程度的变化。研究结果表明，大豆内源基因在三种加工食品中的各个加工过程中都会受到不同程度的破坏。在豆腐、豆奶、豆粉的加工过程中，片段大小为1883bp的lectin基因仅能在原料中检测到；磨浆、煮浆、均质等工艺，使lectin基因降解至1000bp以下；随着进行的点浆、高温杀菌或喷雾干燥等工艺对lectin基因的降解产生更显著的影响，豆腐终产品中lectin基因的片段大小在500bp以下，豆奶、豆粉中lectin基因片段大小仅为200bp左右。     

Inactivation of trypsin inhibitor,lectin and urease in soybean by hydrothermal treatment

The effects of hydrothermal treating parameters on trypsin inhibitor (TI), lectin and urease activities in whole soybean seeds were investigated by Response Surface Analysis (RSA). Independent variables with equidistant levels examined in this study were the following: treating temperature (levels: 70, 85 and 100°C), treating time (levels: 10, 30 and 50 min), and soaking time (2, 4 and 6 h). The functions between treating parameters and responses values of TI, lectin and urease activities in treated soybean were calculated by multiple, non-linear regression analysis and analysis of variance. Mathematical models were developed in this study to predict TI, lectin and urease activities in soybean during hydrothermal processing and they have been found to be significant (P[%] = 0.1, 1.0, and 0.1, respectively). Differences between the effects of processing parameters on the inactivation of TI, lectin and urease in soybean were observed and they can be seen either from the mathematical models or the typical figures. The modeling of the effects should help in selection of optimal parameters of hydrothermal treatment for destruction of TI. lectin and urease in soybean. Based on the modeling, lectin and urease can be fully inactivated in soybean treated at proper conditions, while remaining TI activity can be expected in soybean treated at any conditions examined in this study.     

Effect of seed lectins from Phaseolus vulgaris on the development of larvae of Callosobruchus maculatus; mechanism of toxicity

Seeds of the kidney bean (Phaseolus vulgaris) are toxic to developing larvae of the bruchid beetle (Callosobruchus maculatus), a major storage pest of many legumes. Insect feeding trials were carried out whereby the albumin and globulin protein fractions from seeds of P. vulgaris were incorporated into artificial seeds. Both fractions were shown to be toxic and to contain haemagglutinating activity, implicating the seed lectins as being involved in seed resistance. Further feeding trials using different P. vulgaris lectin preparations confirmed the toxicity of these lectins and suggested that it was the E-type lectin subunits (erythrocyte-binding) which were the major antimetabolites. Indirect immunofluorescence investigations using monospecific antisera for globulin lectins showed that the lectins, when ingested by the larvae, bound to the midgut epithelial cells. It was suggested that the mechanism of lectin toxicity in this instance is analogous to that known to occur in the rat, namely that the ingested lectin causes disruption of the epithelial cells of the larval midgut leading to breakdown of the transport of nutrients into these cells, and the absorption of potentially harmful substances. This is the first time that evidence for the mechanism of lectin toxicity has been obtained in insects.     

Purification and Characterization of a Lectin from the Seeds of Amaranth (Amaranthus cruentus)

A lectin (ACL) was purified from the seeds of Amaranthus cruentus using affinity chromatography on fetuin-agarose. Apparent homogeneity of the lectin was demonstrated by SDS-PAGE, chromatography on Sephadex G100 and immunoprecipitation. The lectin was a dimer with an estimated molecular weight of 66,000 and a subunit molecular weight of 35,000. ACL-mediated agglutination was inhibited by D-GalNAc and fetuin. Thirty other carbohydrates were non-hibitory. ACL contained 2.2% neutral carbohydrate and relatively high levels of aspartic acid, glutamic acid, serine and glycine. The purified lectin was relatively heat labile retaining approximately 10% of its original activity (titer) after 5 min at 70°C and after just 1 min at 100°C.     

Lectins of Lablab purpureus seeds

A column of chitin was utilized to separate four lectins (hemagglutinating activity) from the seeds of (Lablab purpureus L) Sweet. Two of these activities, which were bound by chitin and were also strongly inhibited by N-aeetyl-D -glucosamine, were differentiated according to their ionic properties: one is a basic (C2-S1) and the other is an acidic (C2-S2) lectin. A third N-acetyl-D -glucosamine binding lectin (Cl-2) is also acidic in nature but showed a lower binding capacity towards this sugar than C2-S2. A fourth lectin (C1-1S2) was strongly inhibited by galactose and has an acidic character. The lectin is formed by subunits of 39000 and 44000 kDa.     

豆类植物凝集素抗营养机理研究

植物凝集素是植物在长期进化过程中形成抵御病虫害和动物消化主要成分之一,因此对动物具有较强抗营养作用;该文介绍豆类植物凝集素,并阐述其抗营养机理。     

CLONING, EXPRESSION AND CHARACTERIZATION OF NOVEL LECTIN FROM ORYZA SATIVA

A lectin gene homolog of Oryza sativa was successfully cloned and expressed in Escherichia coli. The deduced amino acid sequence of the protein product showed a significant similarity with known chitin‐binding lectins. Most of the recombinant lectin was found in an insoluble aggregated form as inclusion bodies and only a small part was in the culture medium in a soluble active form. Functional recombinant lectin was recovered from the inclusion bodies by solubilization with 8 M urea in Tris/HCl buffer, pH 7.0 and renaturation by 10‐fold dilution in the same buffer. The recombinant lectin with His‐tag was simply purified to homogeneity by the process of affinity chromatography and was obtained with a yield of 6–8 mg/L culture. The recombinant lectin was a homo‐dimer composed of 22 kDa. The hemagglutination activity of the recombinant lectin was optimal at pH 4.0–7.0 and it was very sensitive to inhibition by N‐acetylneuraminic acid and thyroglobulin.     

A mannose-binding protein from the cell surface of flocculent Saccharomyces cerevisiae (NCIM 3528): its role in flocculation

A cell surface lectin was isolated and purified to homogeneity from the cell walls of a highly flocculent strain of Saccharomyces cerevisiae (NCIM 3528) by chromatography on DEAE-cellulose, phenyl Sepharose and Sephacryl S-300. It showed a molecular mass of 40 kDa on SDS-PAGE. It is an acidic protein with a pI of 4.0 and contains 44% hydrophobic amino acids. The N-terminal sequence up to 10 amino acid residues showed at least 70% homology with the predicted N-terminal sequence of the putative FLO1 as well as FLO5 gene products. The mannose-binding nature of the lectin was indicated by its high affinity and specificity towards the branched trisaccharide of mannose, a ligand which also inhibits the flocculation of yeast cells. Immunofluorescence studies confirmed the presence of lectin on the yeast cell surface and lectin-specific IgGs prevented flocculation of the cells. This cell surface mannose-specific lectin probably plays an important role in flocculation, with the branched trimannoside on the cell wall being the apparent carbohydrate receptor. The N-terminal sequence data gives a primary indication that the lectin could be a product of one of the FLO genes.