反竞争性抑制的非稳态酶动力学布尔函数图解研究

以非稳态酶动力学的布尔函数图形方法,来研究一类反竞争性抑制的非稳态酶动力学问题,推导出此类反应的非稳态酶动力学方程,并对此动力学方程进行了讨论,分析了此类反竞争性制酶反应体系的非稳态酶动力学问题。     

一类非竞争性抑制的非稳态酶动力学布尔函数图解研究

本文以非稳态酶动力学的布尔函数图形方法^[1],来研究一类非竞争性抑制的非稳态酶动力学问题,推导出此类反应的非稳态酶动力学方程,并对此动力学方程进行了讨论,分析了此类非竞争性抑制的非稳态酶动力学的动力学过程。     

Random Bi Bi机制的非稳态酶动力学布尔函数图论研究

本文以非稳态酶动力学的布尔函数图形方法^[1],来研究一类Random Bi Bi机制的非稳态酶动力学问题,推导同此类反应的非稳态酶动力学方程,并对此动力学方程进行了讨论,分析了此类Random Bi Bi机制酶反应体系的非稳态酶动力学方程。     

Ping Pong Bi Bi机制的非稳态酶动力学分布函数图论研究

以非稳态酶动力学的布尔函数图形方法,来研究一类PingPongBiBi机制的非记酶动力学问题,推导出此类反应的非稳态酶动力学方程,并对此动力学方程进行了讨论,分析了此类PingPongBiBi机制酶反应体系的非稳态酶动力学方程。     

非稳态酶活化动力学的布尔函数图论分析

以非稳态酶动力学的布尔函数图形方法研究非稳态酶活化动力学问题,推导出此类反应的非稳态酶动力学方程,并对此动力学方程进行了讨论,分析了酶活化反应体系的非稳态酶动力学过程．     

稳态酶动力学的布尔函数图论分析

使用布尔函数图论分析稳态酶动力学过程,并提供一种简易图形算法。由简单的速率常数组合图形求得分子项中速率常数乘积项的总和。使用类似的方法也可求得分母项中速率常数乘积项的总和。此法的特点是图形鲜明,绘法简易,使用方便(不需画出支撑入树之类的图形,也不需代数运算),结果可靠(不易发生遗漏或错算)。列举无规Bi Uni、有规BiBi 和无规BiBi 酶反应体系作为此图形分析的实例。     

稳态酶动力学的布尔函数图论分析

使用布尔函数图论分析稳态酶动力学过程,并提供一种简易图形算法。由简单的速率常数组合图形求得分子项中速率常数乘积项的总和。使用类似的方法也可求得分母项中速率常数乘积项的总和。此法的特点是图形鲜明,绘法简易,使用方便(不需画出支撑入树之类的图形,也不需代数运算),结果可靠(不易发生遗漏或错算)。列举无规Bi Uni、有规BiBi和无规Bi Bi酶反应体系作为此图形分析的实例。     

酶抑制动力学模型判断中的统计分析

文章用数理统计的方法导出了酶抑制动力学研究中双倒数作图法的统计模型,克服了作图法中主观因素的干扰,建立了判断竞争抑制,非竞争抑制,反竞争抑制,线性混合抑制的统计分析方法。     

黄酮类化合物对cAMP磷酸二酯酶抑制的动力学研究

本文研究了十二种黄酮类化合物对兔心肌中环磷酸腺苷磷酸二酯酶(cAMP-PDE)的动力学,表明它们都属于竞争性抑制类型的,并且还给出了它们的抑制常数Ki值;从Ki值大小可知,黄酮甙元比它们的相应甙具有更强的抑制作用。     

The Effect of Cations on the Amidase Activity of Human Tissue Kallikrein: 1-Linear Competitive Inhibition by Sodium,Potassium, Calcium and Magnesium. 2-Linear Mixed Inhibition by Aluminium

Hydrolysis of D-valyl-L-leucyl-L-arginine p-nitroanilide by human tissue kallikrein (hK1) was studied in the absence and in the presence of increasing concentrations of the following chloride salts: sodium, potassium, calcium, magnesium and aluminium. The data indicate that the inhibition of hK1 by sodium, potassium, calcium and magnesium is linear competitive and that divalent cations are more potent inhibitors of hK1 than univalent cations. However the inhibition of hK1 by aluminium cation is linear mixed, with the cation being able to bind to both the free enzyme and the ES complex. This cation was the best hK1 inhibitor. Aluminium is not a physiological cation, but is a known neurotoxicant for animals and humans. The neurotoxic actions of aluminium may relate to neuro-degenerative diseases.     

鸭肝脂肪酸合成酶的NADPH底物抑制及作用动力学

己知动物脂肪酸合成酶的底物乙酰辅酶Ａ和丙二酰辅酶Ａ具有竞争性双底物抑制的乒乓机制。实验发现鸭肝脂肪酸合成酶的第三个底物ＮＡＤＰＨ也具有底物抑制,并研究了它的规律及与ＮＡＤＰＨ有关的稳态动力学。发现对于该酶的全反应,增加丙二酰辅酶Ａ浓度,降低环境盐浓度,均使ＮＡＤＰＨ底物抑制减少。但以ＮＡＤＰＨ作底物的酮酰还原和烯酰还原二步单独反应以及包含四步单独反应的乙酰乙酰辅酶Ａ还原反应都无ＮＡＤＰＨ底物抑制现象。ＮＡＤＰＨ底物抑制对丙二酰辅酶Ａ为竞争性,丙二酰辅酶Ａ底物抑制对ＮＡＤＰＨ为非竞争性。在全反应中ＮＡＤＰＨ和丙二酰辅酶Ａ之间发现为乒乓机制,在乙酰乙酰辅酶Ａ还原反应中,两个底物ＮＡＤＰＨ和乙酰乙酰辅酶Ａ之间则表现为序列反应机制。降低环境盐浓度使ＮＡＤＰＨ和丙二酰辅酶Ａ之间的乒乓机制向序列机制转化。在全反应中,ＮＡＤＰ产物抑制相对ＮＡＤＰ为竞争性,对丙二酰辅酶Ａ为非竞争性。     

Glutamate Uptake into Synaptic Vesicles: Competitive Inhibition by Bromocriptine

The ATP-dependent uptake of L-glutamate into synaptic vesicles has been well characterized, implicating a key role for synaptic vesicles in glutamatergic neurotransmission. In the present study, we provide evidence that vesicular glutamate uptake is selectively inhibited by the peptide-containing halogenated ergot bromocriptine. It is the most potent inhibitor of the agents tested: the IC50 was determined to be 22 microM. The uptake was also inhibited by other ergopeptines such as ergotamine and ergocristine, but with less potency. Ergots devoid of the peptide moiety, however, such as ergonovine, lergotrile, and methysergide, had little or no effect. Although bromocriptine is known to elicit dopaminergic and serotonergic effects, its inhibitory effect on vesicular glutamate uptake was not mimicked by agents known to interact with dopamine and serotonin receptors. Kinetic data suggest that bromocriptine competes with glutamate for the glutamate binding site on the glutamate translocator. It is proposed that this inhibitor could be useful as a prototype probe in identifying and characterizing the vesicular glutamate translocator, as well as in developing a more specific inhibitor of the transport system.     

Competitive and uncompetitive inhibitors simultaneously acting on an autocatalytic zymogen activation reaction

The time course of the residual enzyme activity of a general model consisting of an autocatalytic zymogen activation process inhibited by an irreversible competitive inhibitor and an irreversible uncompetitive inhibitor has been studied. Approached analytical expressions which furnish the time course of the residual enzyme activity from the onset of the reaction depending on the rate constants and initial concentration have been obtained. The goodness and limitations of the analytical equations were checked by comparing with the results obtained from the numerical integration, i.e. with the simulated progress curves. A dimensionless parameter giving the relative contributions of both the activation and the inhibitions routes is suggested, so that the value of this parameter determines whether the activation or the inhibitions routes prevail or if both processes are balanced during the time for which the analytical expressions are valid. The effects of the initial zymogen, free enzyme and inhibitors concentrations are analysed. Finally an experimental design and kinetic data analysis is proposed to evaluate simultaneously the kinetic parameters involved and to discriminate between different zymogen activation processes which can be considered particular cases of the general model.     

Inhibition of extracellular lipase from Streptomyces rimosus with 3,4-dichloroisocoumarin

Kinetic characterization of lipase inhibition was performed by activity measurement and mass spectrometry (MS), for the first time with serine-protease inhibitor 3,4-dichloroisocoumarin (DCI). Inhibition of Streptomyces rimosus extracellular lipase (SrLip), a member of the SGNH superfamily, by means of DCI follows the mechanism of two-step irreversible inhibition. The dissociation constant of the noncovalent E?I complex and first-order rate constant for inactivation were determined by incubation (K_i* = 26.6?±?2.8 µM, k₂ = 12.2?±?0.6 min–1) or progress curve (K_i* = 6.5?±?1.5 µM, k₂ = 0.11?±?0.01 min–1) method. Half-times of reactivation for lipase inhibited with 10-fold molar excess of DCI were determined by activity measurement (t_1/2 = 11.3?±?0.2?h), matrix-assisted laser desorption/ionization (MALDI, t_1/2 = 13.5?±?0.4?h), and electro-spray ionization (ESI, t_1/2 = 12.2?±?0.5?h) MS. The active SrLip concentration was determined by incubating the enzyme with near equimolar concentrations of DCI, followed by activity and MS measurement.