Evidence for a novel racemization process of an asparaginyl residue in mouse lysozyme under physiological conditions

We examined chemical reactions in mouse lysozyme after incubation under physiological conditions (pH 7 and 37°C). After incubation for 8 weeks, racemization was observed specifically at Asn127 among the 19 Asp/Asn residues in mouse lysozyme. Furthermore, analysis of the primary structure showed that the racemized residue was not Asp, but Asn, which demonstrates that deamidation and isomerization did not occur. These results mean that this racemization occurs without forming a succinimide intermediate. This is the first example of D-asparaginyl formation in a protein occurring during the racemization process under physiological conditions.Received 16 September 2004; received after revision 26 October 2004; accepted 12 November 2004     

Ethanol inhibits insulin expression and actions in the developing brain

Ethanol-induced cerebellar hypoplasia is associated with inhibition of insulin-stimulated survival signaling. The present work explores the mechanisms of impaired insulin signaling in a rat model of fetal alcohol syndrome. Real-time quantitative RT-PCR demonstrated reduced expression of the insulin gene in cerebella of ethanol-exposed pups. Although receptor expression was unaffected, insulin and insulin-like growth factor (IGF-I) receptor tyrosine kinase (RTK) activities were reduced by ethanol exposure, and these abnormalities were associated with increased PTP1b activity. In addition, glucose transporter molecule expression and steady-state levels of ATP were reduced in ethanol-exposed cerebellar tissue. Cultured cerebellar granule neurons from ethanol-exposed pups had reduced expression of genes encoding insulin, IGF-II, and the IGF-I and IGF-II receptors, and impaired insulin- and IGF-I-stimulated glucose uptake and ATP production. The results demonstrate that ethanol inhibits insulin-mediated actions in the developing brain by reducing local insulin production and insulin RTK activation, leading to inhibition of glucose transport and ATP production.Received 30 December 2004; received after revision 1 March 2005; accepted 10 March 2005     

5种菌糖化发酵饲料对肉兔日粮中蛋白质利用率的影响

用5种菌(产朊假丝酵母、热带假丝酵母、啤酒酵母、黑曲霉、白地霉)糖化发酵饲料以20%比例部分替代肉兔日粮,对肉兔增质量、料质量比、蛋白质利用率及脏体比等各项指标进行比较分析.结果表明,5种菌糖化发酵饲料可以促进肉兔增质量,降低饲料消耗,提高肉兔日粮中蛋白质利用率,5种菌糖化发酵饲料的饲喂效果优于基础饲料.     

谷氨酰胺转移酶对食物蛋白质成膜性能的影响

研究了添加谷氨酰胺转移酶（TGase）对大豆分离蛋白（SPI）、酪蛋白酸（NaCN）、明胶、乳清蛋白浓缩物（WPC）、小麦面筋蛋白（WG）及花生分离蛋白（PPI）6种蛋白质成膜特性的影响．研究结果表明：在成膜溶液中加入TGase，蛋白质膜的抗拉强度和表面疏水性有不同程度的改善，其中WG，SPI，NaCN和明胶这4种蛋白质膜的抗拉强度分别增加36．2％，17．7％，13．1％和25．6％（P≤0．05）；NaCN，SPI，WPC，WG和明胶这5种蛋白质膜的表面疏水性分别增加216．1％，116．9％，30．5％，26．4％和2．4％（P≤0．05）；同时膜的水分含量、总可溶性物质量及透光率也明显降低；明胶膜、NaCN膜和WPC膜的断裂伸长率分别增加16．3％，72．6％和172．3％，SPI膜和WG膜的断裂伸长率则分别降低7．5％和36．2％．电泳分析表明TGase使6种蛋白质均产生了共价交联．     

Purification and Characterization of an Antibacterial Protein from the Cultured Mycelia of Cordyceps sinensis

0 IntroductionAlnattie mdicfrroobmiala p wriodteei nvsar iheatdy boefe linv ifnogun odr gaanndis ismos--Bacteria[1], fungi[2 ,3], plants[4]and ani mals[5].Those proteins displayed a wide spectrumof anti mi-crobial activity against different species of viruses ,bacteria andfungi .Over the past few years ,several anti microbialpeptides and proteins were foundinfungus ,such asAFP fromAspergillus giganteus[6], Anafp fromAspergillus niger[7], Zygocin fromthe yeastZy-gosaccharomyces bailii[8],an…     

胰酶水解黑麦草叶蛋白条件的研究

用胰酶水解黑麦草叶蛋白,甲醛滴定法测定蛋白质含量,单因素及正交实验优化水解工艺条件,高效液相色谱分析最优条件下得到的水解物中各组分的相对分子质量排布及大小。结果表明胰酶对黑麦草叶蛋白水解的最佳工艺条件为:(E/S)0.06μg/mL,温度38℃,pH8,水解时间为7 h。水解液中有8个组分,其相对分子质量分布在29~9 493.     

人类磷酸泛酰巯基乙胺结合蛋白新基因的分离和鉴定

在对AD293和HEK293进行差减杂交以探索两者在吸附和凋亡特性上的差异时,从AD293的高表达文库中分离得到一段新的cDNA片段.从人类胎脑文库克隆得到该基因,全长2 745 bp,编码的蛋白含518个氨基酸,被预测为磷酸泛酰巯基乙胺结合蛋白.该基因在染色体上定位于2p22.3,包含8个外显子.该cDNA编码的蛋白序列含有一个凋亡抑制蛋白5结构域,外皮蛋白重复片段和铜结合辛肽重复片段.RT-PCR分析显示该基因在人类正常组织和癌组织中广泛表达,但在癌组织中表达量相对较低,提示其可能对细胞凋亡有抑制作用.该基因在进化过程中高度保守.     

绿色荧光蛋白标记的NTE活性域表达载体的构建及表达

利用含有特定限制性内切酶识别位点的引物,通过聚合酶链式反应扩增出人神经病靶标酯酶活性域的编码序列,经T载体克隆测序正确后,双酶切回收特异片段定向插入到增强型绿色荧光表达载体pEGFP-N3中,通过酶切反应鉴定,构建了绿色荧光蛋白标记的神经病靶标酯酶活性域的融合表达载体pNEST-EGFP.采用脂质体转染的方法将其转染到人神经瘤母瘤细胞SH-SY5Y中,用荧光显微镜观察发现神经病靶标酯酶活性域分布于细胞质中,而且没有导致内质网膜的聚集,表明表达载体成功构建和表达.     

熟化大豆粉与高蛋白豆粉中蛋白消化性能比较

采用AIA酸不溶灰分内源指示剂法,以标准的W istar白化大鼠为试验动物,对熟化大豆粉和高蛋白豆粉中的蛋白质进行了表观消化率的测定。结果表明:二者的表观消化率均在80%~90%,它们的直观差距大约1%,经t测验,差异不显著。可以认为:熟化大豆粉和高蛋白豆粉中蛋白质的表观消化率基本相同。