碱性蛋白酶在酪蛋白磷酸肽生产中的研究

阐述了酪蛋白磷酸肽（CPP）的生物学功能及作用机理,研究了在其生产过程中影响碱性蛋白酶（Alcalase）水解因素,包括pH值、温度等,探讨了乙醇浓度和酪蛋白水解度（DH）及分离方法对CPP得率和N／P（摩尔比）的影响。     

水解乳蛋白及酪蛋白对破伤风梭菌产毒力的影响

水解乳蛋白及酪蛋白对破伤风梭菌产毒力的影响胡鸿刘玉明孟红宗晓龙李毅恒农业部兰州生物制品厂兰州７３００４６在破伤风毒素培养中，用１０％水解乳蛋白制造的产毒培养基（Ⅰ号产毒培养基）进行产毒培养，产毒能力较低，而用酪蛋白消化液制造的产毒培养基（Ⅱ号产毒培养...     

酪蛋白磷酸肽功能研究进展

近年来，已有许多具生物活性的多肽经蛋白质消化而被辩认出来，生物活性肽是近年来国内外动物营养研究的热点之一。酪蛋白磷酸肽（CaseinPhosphopeptides，CPP）是以牛奶酪蛋白为原料，经过单一或复合蛋白酶的水解，再对水解产物分离纯化后得到的含有磷酸丝氨酸簇的天然生理活性肽。CPP是目前唯一促进钙吸收的活性肽，     

酪蛋白磷酸肽生产工艺研究初探

对CPP制取工艺及产品检测进行了初步的研究 :采用胰蛋白酶水解酪蛋白制备CPP ,水解条件为 :[E]/ [S]=0 82 % ,pH =7.5 ,T =48℃ ,t=2h。分离条件为 :调节pH =6 .5 ,加入CaCl2 、乙醇后静止 4～ 8h。应用SephadexG—2 5柱层析和SDS -PAGE对CPP样品进行含量和纯度测定 ,使用双缩脲法和钼酸法分别测定样品CPP中的N、P含量 ,所得产品N/P摩尔比为 7.5 8～ 7.6 5 ,CPP得率为 16 .1%～ 16 .5 %。     

牛乳源酪蛋白糖巨肽工业化分离方法

酪蛋白糖巨肽（简写CGMP）是从干酪生产副产物乳清中分离得到的.当牛乳中κ-酪蛋白被凝乳酶水解时,可产生2种肽,较大的肽叫副-κ-酪蛋白（含1～105残基片段）,具有不溶性,变成干酪凝块的一部分,较小的肽（含106～169残基片段）具有可溶性,变成乳清的一部分.     

酪蛋白磷酸肽及其营养作用

酪蛋白磷酸肽(CaseinPhosphopeptides,CPP)是以牛奶酪蛋白为原料,经过单一或复合蛋白酶的水解,再对水解产物分离纯化后得到的含有磷酸丝氨酸簇的天然生理活性肽(Nicholas,1997)。它是多种长度不同的短肽混合物,主要分布于αs1-、αs2-和β-酪蛋白等牛乳蛋白的不同区域,周杏琴等     

酪蛋白磷酸肽的研究及展望

酪蛋白磷酸肽(CPP)是从牛奶的酪蛋白中提取的一种生物活性肽,可有效地促进Ca,Zn,Fe等矿物元素的吸收。并就国内外对酪蛋白磷酸肽的研究及在畜牧业上的展望作一综述。     

HPLC测定NaOH水解法碘化酪蛋白中MIT、DIT和T4

建立了氢氧化钠水解法碘化酪蛋白中MIT、DIT和T4的高效液相色谱检测方法。在考察的浓度范围内（0.1～20μg/mL）,MIT、DIT和T4均保持较好的线性（r〉0.999）;检出限分别为0.5ng（MIT）和0.25ng（DIT,T4）;定量限分别为1.0ng（MIT）和0.5ng（DIT,T4）。碘化酪蛋白经4mol/L的氢氧化钠溶液110℃水解,水解时间在16～32h,MIT、DIT和T4得率基本保持稳定。定量测定结果和水解稳定性试验显示,MIT和DIT较T4有显著的高含量和高稳定性,更适合用作监测碘化酪蛋白的标识物。     

国际科技资讯

中国研究乳糖糖基化酪蛋白水解物的糖基化位点及其生物活性在牛乳的热加工过程中,蛋白质和乳糖发生美拉德反应,生成糖基化蛋白质。中国研究人员制备乳糖糖基化酪蛋白化合物,用胰蛋白酶水解,得到的糖基化酪蛋白酸盐(glycated caseinate,GCN)水解物的乳糖含量为10.8 g/kg蛋白质。     

消减牛乳酪蛋白致敏性蛋白酶的筛选

以酪蛋白为研究对象，选取复合风味蛋白酶、胰蛋白酶、胰凝乳蛋白酶、碱性蛋白酶、木瓜蛋白酶、菠萝 蛋白酶和中性蛋白酶共7 种食品级蛋白酶，对牛乳酪蛋白进行酶解。通过牛乳过敏患者血清池，评估酶解产物致敏 原性，同时结合水解产物的分子质量分布、水解度、残留表位信息等指标，筛选出最适合用于生产低致敏酪蛋白产 品的蛋白酶。结果表明：在相同条件下经胰凝乳蛋白酶、复合风味蛋白酶处理后酪蛋白与特异性抗体结合能力降低 程度最大，可用于后续低致敏酪蛋白制备的候选蛋白酶；结合T细胞表位预测结果，对酪蛋白水解产物进一步分析 发现，酪蛋白经过胰凝乳蛋白酶酶解后，仅剩余1 条大于9 个氨基酸的T细胞表位肽段LHSMKEGIHAQQK。     

牦牛乳酪蛋白酶解产物二肽基肽酶-Ⅳ抑制活性和特性分析

以牦牛乳酪蛋白为原料,利用碱性蛋白酶、木瓜蛋白酶和胰蛋白酶制备酪蛋白酶解产物,研究其二肽基肽酶-Ⅳ(dipeptidyl peptidase-Ⅳ,DPP-Ⅳ)抑制活性和理化特性.以DPP-Ⅳ抑制率为指标,研究水解时间和蛋白酶的种类对酶解产物DPP-Ⅳ抑制活性的影响,以水解度、三氯乙酸氮溶解指数(trichloroacetic acid-nitrogen soluble index,TCA-NSI)、溶解性和灰分含量为指标,评价酶解产物的理化特性.结果表明:对于相同水解时间点获得的酶解产物,木瓜蛋白酶酶解产物的DPP-Ⅳ抑制活性显著高于其他2种蛋白酶的酶解产物(P＜0.05).利用木瓜蛋白酶水解0.50 h的酶解产物具有最高的DPP-Ⅳ抑制活性(抑制率可达(53.95±1.57)％)、较高的水解程度以及最低的灰分含量.说明利用蛋白酶水解技术能够使牦牛乳酪蛋白中具有DPP-Ⅳ抑制活性的多肽释放,木瓜蛋白酶酶解产物可作为功能性乳基料用于功能性食品的开发.     

牛乳酪蛋白初级抗菌肽粉乳基料的制备

为制备抗菌活性较好的肽粉乳基料,以新鲜牛乳为原料提取酪蛋白,以酪蛋白酶解物对大肠杆菌、沙门氏菌和金黄色葡萄球菌的抑菌圈直径为指标,从木瓜蛋白酶、碱性蛋白酶、中性蛋白酶和胰蛋白酶中筛选出一种蛋白酶水解牛乳酪蛋白,并通过单因素试验和正交试验确定该酶水解牛乳酪蛋白优化水解条件。结果表明：木瓜蛋白酶水解牛乳酪蛋白,其酶解物对3种菌均有较好的抑制作用;优化水解工艺条件为：酶解温度50℃、酶解时间4.5h、加酶量4500U/g、pH5.5、底物质量浓度6g/100mL;牛乳酪蛋白酶解物及初级肽粉乳基料稳定性均较好。     

Proteolytic inactivation of simian-11 rotavirus: a pilot study

In an effort to develop alternate disinfectants for rotaviruses, pilot studies were conducted to determine if bacterial proteases could render simian-11 (SA-11) rotavirus non-infectious. SA-11 was found to be fairly temperature resistant, retaining a low-level of infectivity following 65 degrees C treatment for 2h at pH 8.5. It also resisted pH 8.5-5 at 45 degrees C for 2h. Alcalase, an alkaline protease, was the most effective of the various proteases (alcalase, durazym, neutrase, and savinase) tested. To analyze specific parameters for alcalase, SA-11 virus (10(5.5) median tissue culture infective dose/ml original titer) was treated at pH 6, 25 and 15 degrees C (simulated field conditions), with 0.1 and 1.0% alcalase. At pH 6.0 and 15 degrees C, 0.1% alcalase reduced SA-11 titer by 0. 75 log in 24h, and by 1.25 log in 120h. At 25 degrees C and pH 6.0, 0.1% alcalase reduced the titer by 2.25 log after 24h, and by 2.75 log in 120h. At pH 6.0 and 15 degrees C, 1% alcalase reduced SA-11 titer by 1.50 log in 24h and by 1.75 log in 120h. At the same enzyme concentration and pH, but at 25 degrees C the titer was reduced by 2. 75 log in the first 24h and by 3.25 log at 120h. These results show that the alkaline protease alcalase is capable of inactivating SA-11 virus to a certain degree depending on conditions. Further definition of operating parameters, demonstration of inactivation under field conditions and analysis whether the demonstrated degree of inactivation would decrease calf morbidity and mortality remain to be explored at this time.     

The in vitro antioxidant properties of alcalase hydrolysate prepared from silkie fowl (Gallus gallus) blood protein

Two types of proteins including blood plasma protein and blood cell protein were isolated from silkie fowl (Gallus gallus) blood and hydrolyzed using alcalase for 0, 2, 4 and 6 h. The blood plasma protein hydrolysate (BPH) and blood cell protein hydrolysate (BCH) were analyzed for pH value, peptide content and antioxidative properties. The significantly higher peptide contents were observed in BPH than that of BCH, which showed that blood plasma protein was more suitable to hydrolysis by alcalase than blood cell protein. Both BPH and BCH showed strong 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical‐scavenging activity and Fe²⁺ chelating ability. BPH at 4 h of hydrolysis (BPH4) demonstrated significantly higher antioxidant capacity than those treated by alcalase in most of the assays. The BPH4 was separated using ultra‐filtration and assessment of the fractions and indicated that low molecular weight of peptides (< 3 kDa) possessed greater DPPH scavenging activity, Fe²⁺ chelating ability and inhibitory activity of lipid peroxidation. These results show that BPH has the potential to be ingredients in the food industry as a replacement of synthetic antioxidants.     

Nitrogen balance in lambs fed a high-concentrate diet and infused with differing proportions of casein in the rumen and abomasum

Twenty-five wether lambs (34 +/- 0.9 kg) fitted with ruminal and abomasal infusion catheters were used in a completely randomized design to determine the effects of differing proportions of ruminal and abomasal casein infusion on N balance in lambs fed a high-concentrate diet (85% corn grain, 1.6% N; DM basis) for ad libitum intake. Wethers were infused with 0 (control) or 10.4 g/d of N from casein with ruminal:abomasal infusion ratios of 100:0, 67:33, 33:67, or 0:100% over a 14-d period. Feed, orts, feces, and urine were collected over the last 5 d. Total N intake and excretion were greater (P < 0.01) in lambs infused with casein than in controls; however, N retention did not differ in lambs infused with casein compared with controls, suggesting that N requirements were met without casein supplementation. Total N intake and total N excretion did not differ among casein infusion treatments. Urinary N excretion decreased linearly (P = 0.07) with decreasing ruminal infusion of casein. Site of casein infusion quadratically (P = 0.06) influenced N retained (g/d), with the greatest retention observed in the 33:67 ruminal:abomasal infusion treatment. Dry matter intake from feed decreased from 1,183 to 945 g/d (P = 0.02) in lambs infused with casein compared with controls, but apparently digested DM did not differ among treatments. These data indicate that decreasing the ruminal degradability of supplemental protein above that required to maximize N retention results in decreased urinary excretion of N without greatly affecting apparent diet digestion.     

日粮营养水平对奶牛乳中酪蛋白含量影响的研究进展

酪蛋白是乳蛋白的主要成分,不仅营养丰富,且其水解产物对机体有重要调节作用。影响酪蛋白含量的因素主要有遗传、泌乳阶段、日粮营养水平及其组成等,其中通过调控日粮营养水平来提高乳中酪蛋白含量是一种较为常见的技术手段,对提高饲料利用率及改善乳品品质具有重要意义。作者综述了不同日粮营养水平对奶牛乳中酪蛋白含量的影响,以期为生产实践中提高奶牛乳中酪蛋白含量提供理论基础。     

ORIGINAL ARTICLE: Bioavailability of lysine for kittens in overheated casein is underestimated by the rat growth assay method*,†

Growth assays were performed to determine lysine bioavailability for kittens and rats in untreated and heated casein; these values were compared with estimates obtained with an in vitro method. Body weight, food intake, nitrogen and dry matter digestibility, and plasma lysine were determined during an 80‐day growth trial using kittens (n = 16). Body weight and food intake were determined during a 21‐day growth trial using weanling rats (n = 80). The growth data showed bioavailable lysine to be 102.4% and 100.2% (for untreated casein) and 66.1% and 51.7% (for heated casein) for kittens and rats, respectively. There was no relationship between plasma lysine and dietary lysine concentrations for kittens. There were no significant differences in nitrogen or dry matter digestibility among diets for kittens. The chemically reactive lysine content of untreated casein was 99.6%, and of heated casein was 67.1%. Heat treatment of casein resulted in significantly decreased lysine bioavailability as estimated by all methods. For untreated casein, both growth assays showed good agreement with the in vitro method for available lysine. For heated casein, the rat growth assay significantly underestimated bioavailable lysine as determined in kittens while the in vitro method closely approximated this value for the cat.     

Casein hydrolyzate intramammary treatment improves the comfort behavior of cows induced into dry-off

The effectiveness of casein hydrolyzate as mean to improve the welfare of cows induced into involution was tested in high yielding cows induced into dry-off by abrupt cessation of milking. Treatment with casein hydrolysate prevented build up of udder pressure in cows induced into dry off and was clearly associated with signs (lying behavior and step numbers) that they were calmer and more comfortable than cows induced into dry off by the conventional means. We conclude that treatment with casein hydrolyzate is a viable treatment tool that can prevent the suffering associated with drying-off of high-yielding modern dairy cows.     

蚕蛹不同溶解性蛋白的营养学评价及酶解物对血管紧张素转换酶的抑制活性

分别对缫丝蚕蛹中的水溶性和碱溶性蛋白组分进行营养学评价,为高效开发蚕蛹食品提供依据;通过蚕蛹蛋白酶解产物对血管紧张素转换酶(ACE)的体外抑制活性试验,探讨蚕蛹蛋白作为天然降压药品原料的利用潜力。营养学分析表明:蚕蛹蛋白水溶性和碱溶性组分中的氨基酸种类齐全,且必需氨基酸占总氨基酸的质量分数分别为41.2%和39.2%,明显高于WHO推荐的氨基酸组成模式(>36%);蚕蛹水溶性蛋白有第1～第4限制性氨基酸(依次为亮氨酸、异亮氨酸、缬氨酸和苏氨酸),而蚕蛹碱溶性蛋白仅有第1和第2限制性氨基酸(依次为蛋氨酸+胱氨酸、异亮氨酸),2种溶解性蛋白的生物效价均较低,在开发利用中,应补充限制性氨基酸或与其它蛋白搭配使用,以提高产品的营养价值。体外ACE抑制活性试验表明,蚕蛹的水溶性蛋白和碱溶性蛋白的碱性蛋白酶酶解产物均具有较强的ACE抑制活性,IC50值分别为0.121、0.113 mg/mL,2种蛋白有可能成为降血压肽生产原料。