共查询到20条相似文献，搜索用时 15 毫秒
1.
[目的]寻找安全、高效的酪氨酸酶抑制剂。[方法]以酶抑制动力学为跟踪方法,考察了苹果渣提取物对酪氨酸酶的抑制作用,并将其用于马铃薯的抗褐变。[结果]苹果渣提取物对酪氨酸酶的抑制作用为不可逆抑制,苹果渣提取液浓度为2.0 g/L时,对酪氨酸酶的抑制率高达90.0%,对马铃薯浆褐变的抑制率高达86.8%。[结论]苹果渣提取物对酪氨酸酶的抑制作用为果蔬的抗褐变开辟了一条新途径,具有较大的开发价值。 相似文献
2.
瓯江彩鲤酪氨酸酶基因的克隆与序列分析 总被引：2，自引：1，他引：1
瓯江彩鲤(Cyprinus carpio var.color)是分布在我国瓯江流域的一种鲤科鱼类,色彩艳丽,体形优美,深受人们喜爱。瓯江彩鲤有5种基本体色:"全红"、"大花"、"麻花"、"粉玉"和"粉花",是研究鱼类体色遗传的良好材料和理想模型。酪氨酸酶(tyrosinase)是影响黑色素合成的关键酶,其转录的提前终止会导致黑色素无法合成。采用RACE技术从瓯江彩鲤皮肤转录本中克隆5种体色酪氨酸酶基因全序列,并对序列进行分析。发现在瓯江彩鲤的5种体色中,酪氨酸酶基因cDNA序列长度存在差异:"全红"为2 100 bp,"麻花"为2 107 bp,"大花"为2 073 bp,"粉玉"为1 976 bp,"粉花"为2 111 bp;且每种体色都存在两种类型酪氨酸酶基因(TYR-1,TYR-2)的转录。这两种酪氨酸酶基因mRNA所翻译成的氨基酸序列仅在一二级结构上有所差异,而在结构域和三级结构上不存在差异。但酪氨酸酶基因的这些差异是否与瓯江彩鲤体色相关还有待后续的证明。研究亮点:在国内外首次克隆了鲤的酪氨酸酶基因,发现不同体色瓯江彩鲤均转录完整的酪氨酸酶基因,且每种体色都存在两种酪氨酸酶的mRNA转录。揭示了5种体色瓯江彩鲤酪氨酸酶基因的序列差异,对进一步研究该基因与体色的关系提供了依据。 相似文献
3.
[目的]研究酪氨酸酶的活性,为防止马铃薯及其他舍酪氨酸酶的水果和蔬菜等发生褐变提供参考。[方法]以马铃薯为原料,利用分光光度法测定酪氨酸酶的活性;为确定提取酪氨酸酶的适宜条件,测定不同温度和不同pH值对酶活性影响。[结果]结果显示,多巴溶液的吸收光谱最大吸收峰λmax为480nm,随着时间的增大吸光度变化趋于稳定。以此建立动力学曲线,由曲线的斜率可计算出酪氨酸酶的活性,并由试验得出酪氨酸酶的活性受温度和溶液的pH值影响较大。因此,提取和测定酪氨酸酶的活性时的适宜条件为：可见波长λmax为480nm,温度控制在30℃,pH值6．5。[结论]为保障酪氨酸酶的活性,在提取和测定时应选择适宜的条件。 相似文献
4.
酪氨酸酶是合成黑色素细胞的关键酶,为了探讨竹笋壳黄酮提取物对酪氨酸酶活性的影响,对竹笋壳中的黄酮类物质进行提取纯化,并采用酶动力学方法研究了笋壳黄酮提取物对酪氨酸酶单酚酶和二酚酶的抑制作用。结果表明:笋壳黄酮提取物导致单酚酶和二酚酶活力下降50%的抑制剂浓度(IC50)分别为5.6和4.6mg/mL;笋壳黄酮提取物对酪氨酸酶单酚酶的迟滞时间有明显的延长效应,8.0mg/mL的笋壳黄酮提取物可使单酚酶的迟滞时间从1.4min延长到4.2min;笋壳黄酮提取物对酪氨酸酶二酚酶的抑制作用表现为混合型可逆抑制,笋壳黄酮提取物对游离酶的抑制常数(Ki)为3.1mmol/L,对酶底物络合物的抑制常数(Kis)为5.7mmol/L;笋壳黄酮提取物对酪氨酸酶单酚酶和二酚酶均有抑制作用。 相似文献
5.
Li Q Gao KQ Meng Q Clarke JA Shawkey MD D'Alba L Pei R Ellison M Norell MA Vinther J 《Science (New York, N.Y.)》2012,335(6073):1215-1219
Iridescent feather colors involved in displays of many extant birds are produced by nanoscale arrays of melanin-containing organelles (melanosomes). Data relevant to the evolution of these colors and the properties of melanosomes involved in their generation have been limited. A data set sampling variables of extant avian melanosomes reveals that those forming most iridescent arrays are distinctly narrow. Quantitative comparison of these data with melanosome imprints densely sampled from a previously unknown specimen of the Early Cretaceous feathered Microraptor predicts that its plumage was predominantly iridescent. The capacity for simple iridescent arrays is thus minimally inferred in paravian dinosaurs. This finding and estimation of Microraptor feathering consistent with an ornamental function for the tail suggest a centrality for signaling in early evolution of plumage and feather color. 相似文献
6.
[目的]对泰山赤鳞鱼中酪氨酸酶的活性和表达差异进行研究。[方法]以泰山赤鳞鱼为材料,运用聚丙烯酰胺凝胶电泳与生化染色技术、分光光度技术和酶组织化学技术对赤鳞鱼雌、雄个体9种组织中的酪氨酸酶进行了分析研究。[结果]酪氨酸酶在雌、雄赤鳞鱼的肝胰脏、肠和脾组织中均有存在;同时在雄性赤鳞鱼的胆中也有分布。赤鳞鱼各组织中酪氨酸酶的活性大小存在较大差异。其中,雌雄性赤鳞鱼的脾脏中活性最强,但其活性低于雌性鱼脾中的酪氨酸酶活性。酶组织化学结果显示赤鳞鱼的脾脏、肠、肝胰脏和胆中都存在较强的酪氨酸酶阳性信号,而且脾中的阳性信号最强。[结论]该研究是关于泰山赤鳞鱼酪氨酸酶组织定位研究的首次报道,为进一步了解赤鳞鱼酪氨酸酶的功能提供了理论依据。 相似文献
7.
Huiqin Zheng Xianglong Li Rongyan Zhou Lanhui Li Xiuli Guo Jingfen Kang Dongfeng Li 《Frontiers of Agriculture in China》2010,4(1):109-115
As one member of the tyrosinase-related family directly involved in the production of melanin, TYRP1 is involved in not only melanogenesis but also prevention of melanocyte death, stabilizing tyrosinase and helping determine
the shape of melanosomes, etc. Multi-species sequence comparisons showed that there were two evolutionally conserved non-coding
regions (from −1306 to −733 and from −642 to −515 according to AL138753) upstream of translational initiation sites, representing
putative regulatory regions subject to subsequent experimental tests. Coding sequence length variation and genetic diversity
analysis showed that Felis catus, Homo sapiens and Canis familiaris had more genetic diversities than the other species for TYRP1, especially Felis catus that could be a better choice for studying the TYRP1-associated genetic basis underlying the color diversity. As a 75 kDa type-1 transmembrane glycoprotein, mature TYRP1 possesses
about 17 kDa modifying components, whose function predominantly depends on the existing glycosyl-groups and the Cu components.
In addition, the mutated amino acids within species and the highly conserved amino acids among species were listed in our
paper. 相似文献
8.
目的 观察不同浓度湘西龙山百合提取液对小鼠B-16细胞细胞活力、黑色素含量、酪氨酸酶活性的影响。方法 选用同一传代小鼠B-16黑色素瘤细胞并分组,分别加入不同浓度百合提取液、维生素C二种溶液作用3 d后,用MTT法测定B-16细胞活力;用Maeda等的方法测定B-16细胞酪氨酸酶活性;用Victoria等的方法测定B-16细胞黑色素含量。结果 湘西龙山百合提取液对小鼠B-16细胞的酪氨酸酶活性、黑色素合成的抑制作用明显强于维生素C,组间差异有统计学意义（P<0.05）,且其抑制作用随浓度的增加而增加;同时湘西龙山百合提取液其细胞毒性作用同样强于维生素C,组间差异有统计学意义（P<0.05）。结论 百合提取液对B-16细胞的生长、酪氨酸酶活性和黑色素合成的抑制作用强于维生素C,其抑制作用与浓度呈正相关。 相似文献
9.
[目的]探讨天麻素对体外培养的B16鼠黑素瘤细胞黑素合成的影响及其作用机制。[方法]选择不同浓度的天麻素作用于体外培养的小鼠B16黑素瘤细胞,测定细胞黑素生成量,通过测定天麻素对蘑菇酪氨酸酶活性的影响,初步探讨天麻素影响黑色素形成的机制。[结果]当浓度大于15 mmol/L时,天麻素能抑制B16黑素瘤细胞黑色素形成和酪氨酸酶活性,且呈浓度依赖性。天麻素对蘑菇酪氨酸酶的半抑制浓度(IC50)为(69.37±9.22)mmol/L,对酪氨酸酶的抑制作用表现为混合型可逆抑制,抑制常数Ki=(123.8±20.2)mmol/L,提示天麻素可能通过抑制酪氨酸酶活性抑制B16细胞黑色素的形成。[结论]天麻素可作为一种潜在的色素障碍性疾病治疗药物。 相似文献
10.
[目的]对石榴皮中有效成分进行提取,并对提取物的增白效果进行研究。[方法]以石榴皮为原料,通过单因素试验确定石榴皮中有效成分提取的最佳工艺,同时检测其提取物对酪氨酸酶的抑制作用,探讨石榴皮中有效成分的增白效果。[结果]超声波提取石榴皮中有效成分的最佳条件是:1∶20料液比,提取温度60℃,提取液60%乙醇溶液,超声波处理强度7,处理时间40 min,在此条件下提取得到的石榴皮提取物对酪氨酸酶具有较强的抑制作用。普通溶剂提取法所得提取物对酪氨酸酶的抑制率为60%左右,而在超声波辅助提取最佳条件下得到的提取物对酪氨酸酶活性抑制率达90%;同时提取物对酪氨酸酶的抑制作用随着提取物的浓度增大而增高,最高可达100%。[结论]为将石榴皮开发为美白化妆品的天然绿色原料提供了一定的理论依据。 相似文献
11.
Comparison of structural and physicochemical properties of potato protein and potato flour modified with tyrosinase 
下载免费PDF全文
下载免费PDF全文 ZHU Yu YUAN Yu-han MEI Li-ping DING Shuang-kun GAO Yu-chen DU Xian-feng GUO Li 《农业科学学报》2022,21(5):1513-1524
The present study modified potato protein and flour with tyrosinase to promote the diversification of potato staple foods. The results indicated that tyrosinase treatment markedly altered the secondary structure of proteins. After tyrosinase treatment, the maximum decomposition temperature of potato protein and flour increased from 322.32 to 332.40°C and from 294.24 to 299.61°C, respectively. Tyrosinase treatment remarkably reduced the pasting viscosity of potato flour, that is, the peak viscosity, through reducing viscosity, breakdown, final viscosity, and setback by 32.50, 60.98, 13.04, 68.24, and 74.31%, respectively. In contrast, tyrosinase treatment increased the shear resistance and hardness of the protein and flour gels; the maximum stress values of the protein and flour gels increased from 1.48 to 10.1% and from 6.87 to 14.8%, respectively. Furthermore, tyrosinase treatment promoted viscoelastic properties and structural stability of potato protein and flour. These results may provide an important foundation for the development of novel potato staple foods. 相似文献
12.
The regulatory domain of protein kinase C contains an amino acid sequence between residues 19 and 36 that resembles a substrate phosphorylation site in its distribution of basic residue recognition determinants. The corresponding synthetic peptide (Arg19-Phe-Ala-Arg-Lys-Gly-Ala25-Leu-Arg-Gln-Lys-Asn-Val-His -Glu-Val-Lys-Asn36) acts as a potent substrate antagonist with an inhibitory constant of 147 +/- 9 nM. It is a specific inhibitor of protein kinase C and inhibits both autophosphorylation and protein substrate phosphorylation. Substitution of Ala25 with serine transforms the pseudosubstrate into a potent substrate. These results demonstrate that the conserved region of the regulatory domain (residues 19 to 36) of protein kinase C has the secondary structural features of a pseudosubstrate and may be responsible for maintaining the enzyme in the inactive form in the absence of allosteric activators such as phospholipids. 相似文献
13.
[目的]明确不同出菇处理方法对巨大口蘑菌丝体相关酶活性的影响。[方法]以巨大口蘑菌丝体为试验材料,研究几种不同出菇处理方法对其在不同时间内3种酶活性的影响。[结果]能形成原基的3个处理组从菌丝恢复期到原基形成、现蕾阶段,酪氨酸酶活性相对比较稳定,不能形成原基的2个处理组酪氨酸酶先上升后下降,在第9天达到最大值,显著高于其他3个处理组,说明酪氨酸酶过高反而抑制了原基形成;蛋白酶、淀粉酶活性在原基形成前都得到有效的激活作用,酶活性显著高于不能形成原基的2个处理组。[结论]试验结果为实现巨大口蘑从传统的袋子覆土栽培向瓶子无土栽培出菇的转变,了解巨大口蘑形成原基的相关机理提供了理论依据。 相似文献
14.
马铃薯中酪氨酸酶活性测定及研究 总被引：1，自引：0，他引：1
[目的]研究酪氨酸酶的活性,为防止马铃薯及其它含酪氨酸酶的水果和蔬菜等发生褐变提供参考。[方法]以马铃薯为原料,以pH=7.2的Na2HPO4-HCl缓冲溶液为体系,用分光光度计在480nm处测定马铃薯提取液的吸光度,建立曲线,从而得出酪氨酸酶的活性。[结果]在该条件下,所测数据波动小,酪氨酸酶的活性稳定性高。[结论]采用分光光度法测定马铃薯中酪氨酸酶活性,方法简便、准确度高。 相似文献
15.
Resistance to the ABL kinase inhibitor imatinib (STI571 or Gleevec) in chronic myeloid leukemia (CML) occurs through selection for tumor cells harboring BCR-ABL kinase domain point mutations that interfere with drug binding. Crystallographic studies predict that most imatinib-resistant mutants should remain sensitive to inhibitors that bind ABL with less stringent conformational requirements. BMS-354825 is an orally bioavailable ABL kinase inhibitor with two-log increased potency relative to imatinib that retains activity against 14 of 15 imatinib-resistant BCR-ABL mutants. BMS-354825 prolongs survival of mice with BCR-ABL-driven disease and inhibits proliferation of BCR-ABL-positive bone marrow progenitor cells from patients with imatinib-sensitive and imatinib-resistant CML. These data illustrate how molecular insight into kinase inhibitor resistance can guide the design of second-generation targeted therapies. 相似文献
16.
For half a century, successful antifolate therapy against Plasmodium falciparum malaria has been attributed to host-parasite differences in drug binding to dihydrofolate reductase-thymidylate synthase (DHFR-TS). Selectivity may also arise through previously unappreciated differences in regulation of this drug target. The DHFR-TS of Plasmodium binds its cognate messenger RNA (mRNA) and inhibits its own translation. However, unlike translational regulation of DHFR or TS in humans, DHFR-TS mRNA binding is not coupled to enzyme active sites. Thus, antifolate treatment does not relieve translational inhibition and parasites cannot replenish dead enzyme. 相似文献
17.
[目的]研究3,5-二羟基甲苯与L-肌肽对酪氨酸酶活性的抑制作用。[方法]从新鲜蜜梨中提取酪氨酸酶,以邻苯二酚为底物,研究3,5-二羟基甲苯、L-肌肽对酪氨酸酶活性的影响。[结果]3,5-二羟基甲苯与L-肌肽对酪氨酸酶均有一定的抑制作用。[结论]L-肌肽对酪氨酸酶的抑制作用强于3,5-二羟基甲苯。 相似文献
18.
(epsilon)-((gamma)-Glutamyl)lysine has been isolated from enzymatic hydrolyzates of cross-linked human fibrin. This compound was not detected in "non-cross-linked" fibrin prepared with ethylenediaminetetraacetic acid, which inhibits factor XIII; intermediate amounts were observed when the fibrin was prepared with glycine ethyl ester, which inhibits factor XIII competitively. These and ancillary experiments furnish conclusive evidence that epsilon-(gamma-glutamyl)lysine cross-links form in human fibrin during polymerization catalyzed by factor XIII. 相似文献
19.
通过体外蘑菇酪氨酸酶活性的检测,研究了人参皂苷Rb1对体外蘑菇酪氨酸酶的影响;通过细胞增殖率的测定,研究了人参皂苷Rb1对B16黑色素细胞增殖的影响。结果表明:不同浓度Rb1样品对于体外蘑菇酪氨酸酶的抑制率明显低于熊果苷(P0.1),抑制率均在±5%,说明人参皂苷Rb1对于体外蘑菇酪氨酸酶活性没有明显作用;人参皂苷Rb1对B16黑色素细胞增殖的影响随着浓度的变化而变化,当Rb1质量浓度125μg/mL时对B16黑色素细胞增殖有促进作用,125μg/mL时对B16黑色素细胞增殖有抑制作用。 相似文献
20.
Tobacco etioplasts replicate at least twice during light-induced development. Their size is doubled over the same period. The two processes do not show the same kinetics. 5-Fluorodeoxyuridine inhibits chlorophyll synthesis during the normal course of "greening" by inhibiting chloroplast growth. This compound also inhibits cytokinin-induced chloroplast replication. 相似文献