Tamura H, Horiike K, Fukuda H, Watanabe T
Department of Pharmacology I, Tohoku University School of Medicine, Miyagi.
J Biochem. 1989 Feb;105(2):299-306. doi: 10.1093/oxfordjournals.jbchem.a122657.
The mechanism of inhibition of diamine oxidase [DAO, histaminase, amine: oxygen oxidoreductase (deaminating) (copper-containing), EC 1.4.3.6] by aminoguanidine was studied kinetically. The DAO reaction was carried out with putrescine as a substrate in the presence of o-aminobenzaldehyde and followed by the continuous increase in A430. An enzymatic reaction product, 4-aminobutyraldehyde, was spontaneously cyclized to delta 1-pyrroline, which coupled with o-aminobenzaldehyde to give rise to a yellow quinazolinium chromophore [Holmstedt et al. (1961) Biochim. Biophys. Acta 48, 182-186]. First, to measure the initial velocities as accurately as possible, the kinetic relationship between the oxidase reaction rate and the color development rate was formulated. The reaction proceeded linearly in the absence of aminoguanidine, but slowed down time-dependently in its presence. When the color development velocities in the presence of the inhibitor were plotted against time, the plot was nonlinear and there seemed to be at least two phases of the inhibition. Nonlinear least-squares analysis of the data dA430/dt showed that the simplest model that fitted best was a model composed of two species of enzyme-inhibitor complexes: E + I k+1 in equilibrium k-1 EI k+2 in equilibrium k-2 E'I where E is the enzyme, I is aminoguanidine (an inhibitor), and the ks are the rate constants.(ABSTRACT TRUNCATED AT 250 WORDS)
对氨基胍抑制二胺氧化酶[DAO，组胺酶，胺：氧氧化还原酶（脱氨基）（含铜），EC 1.4.3.6]的机制进行了动力学研究。以腐胺为底物，在邻氨基苯甲醛存在下进行DAO反应，随后A430持续增加。酶促反应产物4-氨基丁醛自发环化生成δ1-吡咯啉，其与邻氨基苯甲醛偶联生成黄色喹唑啉发色团[霍尔姆施泰特等人（1961年）《生物化学与生物物理学报》48，182 - 186]。首先，为尽可能准确地测量初始速度，建立了氧化酶反应速率与显色速率之间的动力学关系。在无对氨基胍时反应呈线性进行，但在其存在下随时间减慢。当绘制抑制剂存在下的显色速度对时间的曲线时，该曲线是非线性的，且抑制似乎至少有两个阶段。对数据dA430/dt进行非线性最小二乘法分析表明，拟合得最好的最简单模型是由两种酶 - 抑制剂复合物组成的模型：E + I k + 1处于平衡k - 1 EI k + 2处于平衡k - 2 E'I，其中E是酶，I是对氨基胍（一种抑制剂），ks是速率常数。（摘要截短于250字）
