脲酶

In Chapter 6, an extensive kinetic study of the inhibition of ribonuclease A and papain by urea has been performed. The results suggest that the effect of urea on activities of these enzymes can be well described by the denaturant binding model. The binding constants of urea determined by the present method are nearly identical to that determined from a variety of different studies on model compounds and proteins.

我们在第六章中研究了脲作用下核糖核酸酶A和木瓜蛋白酶的抑制动力学，发现变性剂结合模型可以很好地描述脲对这两个酶活力的影响，而且用我们自己建立的方法测得的脲与蛋白质的结合常数与前人通过对模型化合物和某些蛋白质的研究所获得的数值基本一致。

On the basis of the kinetic equation of substrate reaction in the presence of urea or guanidine hydrochloride, all microscopic kinetic constants for the free enzyme and enzyme-substrate binary and ternary complexes have been determined. The results of the present studies indicate that:①In the presence of urea or guanidine hydrochloride, enzyme-substrate complexes lose their activity less rapidly than the free enzyme. Therefore, both substrates, NADPH and 7, 8-dihydrofolate, protect dihydrofolate reductase against inactivation.②The denaturation of dihydrofolate reductase by urea follows single-phase kinetics, and changes in enzyme activity and tertiary structure proceed simultaneously in the unfolding process, so it may be an"all or none"process.③The GdnHCl-induced unfolding of the dihydrofolate shows a biphasic transition, while the change in the enzyme activity is a single exponential process. The rate constant of inactivation is consistent with that of the fast conformational change. Therefore, the kinetic intermediate of protein unfolding should be a partially folded and inactive form.

我们根据在脲或盐酸胍存在下的底物反应动力学方程求得游离酶和酶底物二元、三元复合物的微观动力学常数，结果表明：①酶-底物二元、三元复合物的失活速度明显慢于游离酶，说明两个底物二氢叶酸和NADPH对酶的失活都具有一定程度的保护作用；②在脲作用下，酶的失活和构象变化均为单指数项过程，而且酶的活力丧失和三级结构变化是同时发生的，说明二氢叶酸还原酶的脲变性可能是一个"全或无"的两态过程；③在盐酸胍作用下，酶的构象变化为两相过程，而失活则是单指数项过程，酶分子构象变化的快相速度常数与失活速度常数基本一致，因此我们认为二氢叶酸还原酶的盐酸胍变性过程中存在一个没有活力、但仍具备一定空间结构的变性中间体。

Methods Seven probe drugs were incubated with or without methyl protodioscin respectively in human microsomes. The specific substrates used in this study were caffeine (CYP1A2), dextromethorphan (CYP2D6), tolbutamide (CYP2C9),-mephenytoin (CYP2C19), chlorzoxazone (CYP2E1), coumarin (CYP2A6) and midazolam (CYP3A4). The concentrations of the substrate metabolites (paraxanthine, dextrorphan, 4-hydroxytolbutamide, 4-hydroxymephenytoin, 6-hydroxychlor-zoxazone, 7-hydroxycoumarin and 1-hydroxymidazolam) were determined by HPLC and LC-MS/MS. Results MPD 1-10 μmolL^(-1 had no significant inhibition on the activities of the seven cytochrome P450 enzymes.

将MPD和CYP450酶7种亚型的特异性探针底物咖啡因(CYP1A2)、右美沙芬(CYP2D6)、甲苯磺丁脲(CYP2C9)、s-美芬妥因(CYP2C19)、氯唑沙宗(CYP2E1)、香豆素(CYP2A6)及咪达唑仑(CYP3A4)与人肝微粒体进行孵化反应，采用HPLC和LC-MS/MS法测定对应的7种代谢产物（1，7-二甲基黄嘌呤、去甲右美沙芬、4-羟基甲苯磺丁脲、4-羟基美芬妥因、6-羟基氯唑沙宗、7-羟基香豆素和1-羟基咪达唑仑）的浓度，通过与对照组比较，确定MPD对以上7种酶活性的影响。

The distribution, properties,structure and regulation of plant allantoinase were reviewed in detail.

文摘：全面综述植物酰脲降解代谢酶的研究现况，概述植物尿囊素酶的分布、性质、结构，以及调节控制，并简介植物尿囊酸酰胺水解酶和脲基乙醇酸酰胺水解酶的研究近况，同时指出待研究的方向。

The biological tests indicate that most of the compounds synthesized have herbicidal activity in a certain degree and several compounds show certain bactericidal activity. Further anti-ALS enzyme test shows that two kinds of novel phosphonic ureas have good anti-ALS enzyme activity.

对合成的部分化合物进行了初步的生物活性测定，所设计的大部分化合物都显示出一定的除草活性，有的具有一定的杀菌活性；对两类膦酰脲化合物进行了离体ALS酶抑制试验，结果表明它们是很好的ALS酶抑制剂，同磺酰脲相当，有希望作为另一类ALS酶抑制剂的先导化合物。

Drought stress changed the correlation of NH4+-N and NO3——N with protease,urease activity,ammonifying bacteria and nitrifying bacteria.

干旱胁迫改变了玉米根际NH4+-N和NO3--N与蛋白酶、脲酶、氨化细菌和硝化细菌的相关性。

The characteristics, the working mechanisms on urease and nitrating inhibition as well as ammonia stability, technological keys, fertilizer product quality, and agricultural effect of compound fertilizer based on humic acid are discussed for the increase in fertilizer efficiency, improvement of agricultural product and raise of crop yield.

阐述腐植酸复混肥的性能，作用机理(脲酶抑制和硝化抑制机理及氨稳定机理)，生产技术要点，产品质量，农用效果(提高肥料利用率，改善农产品品质，提高作物产量)。

Compared with extruded full fat soy bean, the oil of SPFFSB was more stable during storage.

结果表明同膨化工艺相比，热处理大豆的贮藏稳定性好于膨化大豆，KOH氮溶指数和脲酶活性均达到饲用要求。

A new method of using photoactivable ester with azido group was described to immobilize urease on polyether sulfone film surface.

我们利用含芳香叠氮基的光活性酯将脲酶光固定在聚醚砜(Polyether sulfone，pes)膜的表面。

The lime soil from the winter fallow field in which Chinese vetch green manure was once planted and the natural barren field in Guilin Village were taken to determine urease activity and soil fertility of the lime soil.

方法］取桂林毛村常年种植过紫云英绿肥的冬闲田和自然抛荒农田中的石灰土，测定石灰土的脲酶活性和土壤肥力。

I didn't watch TV last night, because it .

昨晚我没有看电视，因为电视机坏了。

Since this year, in a lot of villages of Beijing, TV of elevator liquid crystal was removed.

今年以来，在北京的很多小区里，电梯液晶电视被撤了下来。