苦荞蛋白质的低消化性研究Ⅱ——酶解产物的超微结构分析和分子量分布

苦荞麦蛋白质氨基酸组成平衡,生物价高,并且具有独特的生理功能。体外消化实验表明其蛋白质的消化率较低,通过扫描电镜对四种蛋白质组分酶解产物的超微结构进行观察发现,胃蛋白酶作用于四种组分的方式是不同的,胃蛋白酶不仅可以作用与清蛋白和球蛋白的表面,而且随着水解进程的延长胃蛋白酶还可以作用与清蛋白和球蛋白的内部结构,因此其体外消化率相对较高。而对于醇溶蛋白和谷蛋白,其高级结构相对较为稳定,胃蛋白酶只能作用于其表面,很难作用其内部结构,所以这两种蛋白组分的体外消化率相对较低。此外还通过高效液相对其酶解物的分子量分布进行研究,结果表明,清蛋白和球蛋白的酶解产物分子量相对较低,组分多,酶解程度高。醇溶蛋白酶解物的组成较为简单,这可能是由于被胃蛋白酶作用的位点较少所造成的。而谷蛋白,其酶解物的分子量分布广,高分子量的组分所占比例大,这表明其被酶解的程度相对较低。     

1HNMR研究苯甲酸钠、维生素C及葡萄糖与蛋白质的结合部位

用1HNMR 波谱法研究了苯甲酸钠(SB)、维生素C(VC)及葡萄糖(Glu)分别与牛血清白蛋白(BSA)、胃蛋白酶 (Pepsin)结合的主要部位.结果表明,SB与BSA、Pepsin的结合部位为SB分子中的苯环片段,除静电相互作用外,主要以芳香环间π-π电子堆积作用方式相互结合.VC与BSA、Pepsin的结合部位...     

Antioxidant activities of pepsin hydrolysates of water‐ and salt‐soluble protein extracted from pork hams

The objective of this study was to evaluate the antioxidant activities of pepsin‐digested water‐soluble protein (WSP) and salt‐soluble protein (SSP) extracted from pork ham. WSP and SSP were hydrolysed by pepsin for 2–10 h with 2‐h increments. The protein hydrolysates by pepsin were analysed by sodium dodecyl sulphate‐polyacrylamide gel electrophoresis, and reducing power of the hydrolysates was measured. In addition, antioxidant activity of the hydrolysates was determined using linoleic acid emulsion system. Protein bands with molecular weight higher than 7 kDa in WSP and SSP were completely hydrolysed by pepsin after 2 h of digestion time. WSP hydrolysates (WSPH) and SSP hydrolysates (SSPH) had higher ferric reducing power than controls (WSP and SSP without pepsin digestion). Reducing powers of WSPH were higher than those of SSPH, regardless of digestion time. The oxidative activity of linoleic acid was predominantly inhibited by the addition of WSPH and SSPH, especially 0.5% protein hydrolysate. These results indicate that several functional peptides of pork protein digested by pepsin might have antioxidant activity, and thus they may be used as an antioxidant agent in muscle food system.     

采用盐析及Q Sepharose FF分离纯化酪蛋白胃蛋白酶水解物中的酪蛋白糖巨肽

本文探讨了利用了（NH4）2SO4分级沉淀、透析脱盐及Q—Sepharose FF层析分离纯化酩蛋白的胃蛋白酶水解物中的CGMP的工艺。结果表明：采用60％饱和度的（NH4）2SO4盐析，可从上清液中直接回收高纯度CGMP，得率为0．71％。低饱和度的（NH4）2SO4可有效脱除杂蛋白。脱盐粗提物CGMP Q—Sepharose FF层析条件为：pH8．5、20mmol／L Tris缓冲液平衡上样，用含0．3mol／L NaCl、20mmol、pH7．1的Tris缓冲液洗脱：浓缩物最大上样量为34．2mg蛋白／ml树脂。利用优化的工艺对水解液层析纯化，纯化产物得率约为2．19％（以酪蛋白汁），总结合态唾液酸回收率为87．4％（以酶解液中的唾液酸汁），糖基化度可提高到0．472以上。整个工艺路线简使、快捷、成本较低，适合工业化生产。     

ph‐Dependent Synthesis of Pepsin‐Mediated Gold Nanoclusters with Blue Green and Red Fluorescent Emission

This report demonstrates the first pH‐dependent synthesis of pepsin‐mediated gold nanoclusters (AuNCs) with blue‐, green‐, and red‐fluorescent emission from Au₅ (Au₈), Au₁₃, and Au₂₅, respectively. Pepsin is a gastric aspartic proteinase (molecular weight, 34 550 g/mol) that plays an integral role in the digestive process of vertebrates. It was found that the pH of the reaction solution was critical in determining the size of Au NCs (i.e., the number of gold atoms of AuNCs). Interestingly, enzyme function of pepsin contributes to the formation of these AuNCs. The photo‐stability of the Au₂₅ (or Au₁₃) NCs is much higher than that of Au₅NCs (i.e., Au₂₅ ～ Au₁₃ > > Au₅). The pepsin‐mediated Au₂₅NCs were also found to be useful as fluorescent sensors for the detection of Pb²⁺ ions by enhanced fluorescence and the detection of Hg²⁺ ions by fluorescence quenching. Although the detailed formation mechanisms of these AuNCs require further analysis, the synthetic route using proteinase demonstrated here is promising for preparing new types of fluorescent metal nanoclusters for application in catalysis, optics, biological labeling, and sensing.     

猪血球胃蛋白酶水解物抗氧化活性的研究

以脂质氧化抑制力(LA)、亚铁离子螯合能力(FICP)、二苯代苦味酰肼(DPPH)自由基清除能力(DRSA)为测定指标,探讨了猪血球胃蛋白酶水解物(PDPH)的抗氧化活性。结果表明,PDPH具有极好的亚油酸脂质氧化抑制力(P<0.01)、一定的FICP(P<0.05)和DRSA(P<0.05)。PDPH的脂质氧化抑制力在10μg/mL时为α-生育酚的4.38倍,100μg/mL时为5.50倍;金属离子螯合能力在100μg/mL样品浓度,50μmol/L FeCl2时的螯合率约为10μmol/L EDTA的1.23倍;在10-100μg/m L样品浓度时基本无DRSA,但在500μg/m L的DR-SA为53.8%。     

胃蛋白酶法提取草鱼鳞胶原蛋白的工艺研究

以胃蛋白酶，在酸性条件下对鱼鳞中胶原蛋白进行提取，研究加酶量（E／S）、底物浓度和提取时间3个因素对提取效果的影响。分别通过混合均匀设计和正交实验设计法，最终确定出最佳酶提取条件为：胃蛋白酶30ms／s，3％醋酸80mL/g，恒温（18℃）摇床提取48h。     

酶解谷朊粉制备小麦肽的研究

以小麦蛋白为原料，采用胃蛋白酶制备小麦肽，并对其水解工艺进行优化。以水解度（DH）为响应值，设计了四因素（温度、pH值、底物浓度和加酶量）三水平的中心组合响应面试验。通过优化组合得到最佳水解条件为温度41℃、pH2．00、底物浓度2％、加酶量1500U／g。通过在DH最佳水解条件下进行水解实际检验，其DH为9．4％。     

胶原蛋白的提取工艺研究

探讨了胃蛋白酶法从猪肌腱中提取胶原蛋白的工艺.从酶浓度和酸浓度两个重要影响因素对工艺进行优化.并利用傅立叶变换红外光谱对胶原结构进行鉴定,同时采用高效液相色谱对所提胶原蛋白进行氨基酸组成分析.     

PROPERTIES OF YEAST PROTEINASES

The properties of yeast proteinases, present in the extract of brewer's yeast, were compared with corresponding properties of plant proteinases, pepsin and trypsin in order to find suitable conditions for their activities to be determined independently. The main differences between yeast and plant proteinases were found in their themostability and activity at pH 3·0. In contrast to plant proteinases, yeast proteinases are thermolabile and active at pH 3·0. The proteolytic activity of yeast proteinases in beer is low and may be detected with sensitive methods using radiolabelled protein substrate. Nevertheless, a very wide range of proteolytic activities (67–1082 nkat/litre) was found in samples of unpasteurized beers.