抗菌肽基因异源表达系统研究进展

抗菌肽是机体天然免疫系统的重要组成部分,因具有抗菌谱广、活性稳定、不易产生耐药性等优点而在食品、饲料、农业、医药领域具有重要的应用价值.由于化学合成的成本较高,利用基因工程技术构建高效的生物表达系统成为一个新的途径.综述了抗菌肽在细菌、酵母、植物、动物等表达系统中异源表达的研究进展,为抗菌肽的研究应用提供理论依据.     

Hormonal regulation of metabolism in hepatocytes of the ureogenic teleostopsanus beta

Short-term exposure of isolated toadfish hepatocytes to high concentrations (100 nM) of glucagon, glucagon-like peptide (GLP) or epinephrine significantly increases the rate of lactate gluconeogenesis (1.3-fold) and glycogenolysis (5- to 7-fold). Half-maximal responsiveness to GLP is reached at about 2 nM for gluconeogenesis and 6 nM for glycogenolysis, while the value for glycogenolysis activated by catfish glucagon is 28 nM. Cells do not to respond to 5 nM epinephrine. Norepinephrine, urotensin II and leucine-enkephalin, each applied at 100 nM, increase the rate of glycogenolysis by 1.3 to 1.5-fold. All other hormones tested (vasotocin, isotocin, VIP, methionine-enkephalin, ovine prolactin, -endorphin, APY, salmon insulin) failed to affect metabolic flux through glycogenolysis or gluconeogenesis. None of the hormones altered the rate of urea synthesis or the rate of lactate oxidation by hepatocytes. Although toadfish hepatocytes are responsive to hormonal stimuli, they do not appear to be a useful model to study evolutionary trends in short-term hormonal regulation of urea synthesis. However, the obvious differences in mechanisms of control of urea synthesis in this species compared with ureogenic amphibians and mammals open an intriguing avenue for research.     

The effect of piscidin antimicrobial peptides on the formation of Gram-negative bacterial biofilms

Fish-derived antimicrobial peptides are an important part of the innate immune system due to their potent antimicrobial properties. Piscidins are a class of antimicrobial peptides first described in hybrid striped bass (Morone chrysops x Morone saxatilis) but have also been identified in many other fish species. Previous work demonstrated the broad antimicrobial activity of piscidins against Gram-negative and Gram-positive bacterial species. This study sought to determine the extent to which class I (striped bass piscidin 1, white bass piscidin 1 and striped bass/white bass piscidin 3) and class II (striped bass piscidin 4 and white bass piscidin 5) piscidins inhibit biofilm formation of different Gram-negative bacteria. In general, the class I and II piscidins demonstrate potent activity against Escherichia coli and Flavobacterium columnare biofilms. The class II piscidins showed more activity against E. coli and F. columnare isolates than did the class I piscidins. The piscidins in general were much less effective against inhibiting Aeromonas hydrophila and A. veronii biofilm growth. Only the class I piscidins showed significant growth inhibition among the Aeromonas spp. examined.     

鲶鱼骨酶解物的降血压肽活性研究

以鲶鱼骨蛋白为原料制备ACE抑制肽,采用碱性蛋白酶、中性蛋白酶、木瓜蛋白酶、胰蛋白酶、胃蛋白酶进行酶解,通过体外检测法测定其抑制率,优选出最佳用酶。通过单因素试验和正交试验,确定了碱性蛋白酶酶用量、pH、酶解温度、酶解时间、底物浓度等因素对ACE活性抑制效果的影响。结果表明:利用碱性蛋白酶水解鲶鱼骨,酶用量为500U/g、pH值8.5、温度为60℃、底物浓度为0.33kg/L、时间6h时酶解液对ACE的抑制活性最强,抑制率为88.36%。通过比较,最佳酶解条件下得到的降血压肽的ACE抑制率要高于降血压药尼莫地平和硝苯地平的ACE抑制率。     

不同水平小肽制剂对黑凤鸡生产性能及其血清生化指标的影响

选取 190日龄的产蛋黑凤鸡 135只 ,随机分成 5组。对照组饲喂基础日粮 ,其余 4组分别以 0 .5 %和 0 .3%的小肽制剂添加量替代基础日粮中 30 %或 5 0 %的鱼粉量。结果表明 ,添加量为 0 .5 %的小肽制剂替代基础日粮中 30 %的鱼粉量的试验 1组黑凤鸡的采食量、产蛋性能蛋的品质、饲料利用率均较高 ;小肽添加量为 0 .5 %的试验 1组和 2组黑凤鸡血清BUN水平分别比对照组低 33.33% (P >0 .0 5 )和 7.84 % (P >0 .0 5 ) ,TP含量比对照组分别高 14 .2 4 % (P <0 .0 5 )和 5 .2 2 % (P >0 .0 5 ) ,有利于提高黑凤鸡的生产性能和机体合成蛋白质的能力     

乳蛋白生物活性肽的来源及其生理重要性

乳蛋白经酶解产生的肽类除了具有营养作用外,还具有多种生物活性,包括阿片肽、阿片拮抗肽活性及免疫调节、抗高血压、抗血栓、抗菌、促进矿质元素吸收等活性.综述了这些活性肽在体内、体外及通过微生物作用的产生情况,并对其生理重要性进行了简要论述.     

酶解牛乳蛋白多肽复合果汁乳酒工艺研究

为克服传统乳酒缺陷，该文采用蛋白酶水解法及酒精酵母乳酸菌混合发酵法研究了牛乳蛋白多肽复合果汁乳酒的生产工艺。通过对比和正交试验确定了牛乳蛋白的最佳水解酶、水解条件及牛乳蛋白多肽复合果汁乳酒的发酵条件和配方。结果表明：牛乳蛋白的最佳水解酶是中性蛋白酶，最佳水解条件是：酶用量140 mg/L，温度50℃，pH 6.5，酶解5 h,牛乳蛋白水解最彻底；牛乳蛋白多肽复合果汁乳酒的最佳发酵条件为经中性蛋白酶水解的牛乳，用蔗糖调整其糖度为15%，再配以4%的猕猴桃浓缩汁，添加0.35％ kefir发酵剂在25℃发酵12 h，发酵液中的酒精及总酸含量较高；牛乳蛋白多肽复合果汁乳酒的最佳配方组成是：发酵液60%、糖6%、酸0.28%、甜味剂0.1%、稳定剂0.5%、复合香精0.06%、风味增强剂8 mg/L，乳酒品质最好。     

用于连续制备乳清蛋白ACE抑制肽的酶膜反应器运行条件优化

采用中空纤维膜连续型酶膜反应器制备血管紧张素转移酶(angiotensin converting enzyme,ACE)抑制多肽。在传统酶解工艺条件的基础上,设计出能高效连续制备ACE抑制肽的酶膜反应器,并对此酶膜反应器的运行参数进行了优化,得到能高效制备ACE乳清蛋白源抑制肽的运行条件是:循环流速22.4 L/h,底物质量分数5%,跨膜压力0.07 MPa,酶膜反应器能稳定运行12 h以上,得到乳清蛋白酶解产物的ACE抑制率为30%￣50%。     

合浦珠母贝抗菌肽粗提液制备方法的优化

研究了不同处理方法制备合浦珠母贝外套膜和鳃组织抗菌肽粗提液的抗菌活性,结果表明：以1.0×106cfu·mL^-1无乳链球菌刺激合浦珠母贝14 h以内对其粗提液抗菌活性无显著影响;合浦珠母贝外套膜或鳃组织抗菌肽粗提液制备时,IKAT-18匀浆机的匀浆效果要优于组织匀浆器和研钵。100℃水浴处理组织粗提液10 m in可显著提高其对溶藻弧菌的抗菌活性;反复冻融则会显著降低外套膜组织粗提液的抗菌效果。     

蚕的免疫研究进展

本文介绍了近年来对蚕的免疫研究进展情况。现已发现蚕具有体液免疫和细胞免疫能力。在体液免疫防御系统中,凝集素、溶菌酶和抗菌肽起着重要作用,特别是抗菌肽作用最强,现对其化学本质、分子结构以及诱导其产生的诱导源、动力学等均已弄清。在细胞免疫防御系统中,发现某些血细胞具有免疫力,可吞噬包囊异物或释放趋化因子,进行细胞反应。