Smovzh S A
National Agrarian University of Ukraine, Kyiv.
Ukr Biokhim Zh (1978). 1998 Jan-Feb;70(1):38-44.
The dependence of structural and functional properties of lactate dehydrogenase from the pig muscle (isoenzyme M4) on pH (6.9-8.5) on the effect of different forms of non-protein nitrogen (e.g. urea and ammonium chloride) has been investigated. It was shown that Vmax changes negligibly at pH 6.9-8.5 but K(m) increase markedly with pH elevation. At the alkali value of pH pyruvate inhibition disappeared. We have found that urea and ammonium chloride at the non-saturation concentrations inhibited the activity of lactate dehydrogenase. The inhibition constants (Ki and Ka) for urea and ammonium chloride were obtained from inhibition data. When analysing works of different authors and own results we propose the general model of catalysis of lactate dehydrogenase, which includes the formation of normal enzyme-substrate complex, abortive enzyme-NAD-pyruvate complex and the effect of different effectors, including nitrogen containing substances.
研究了猪肌肉乳酸脱氢酶（同工酶M4）的结构和功能特性在pH值（6.9 - 8.5）范围内对不同形式非蛋白氮（如尿素和氯化铵）作用的依赖性。结果表明，在pH 6.9 - 8.5时Vmax变化可忽略不计，但K(m)随pH升高而显著增加。在碱性pH值下丙酮酸抑制作用消失。我们发现，非饱和浓度的尿素和氯化铵会抑制乳酸脱氢酶的活性。从抑制数据中获得了尿素和氯化铵的抑制常数（Ki和Ka）。在分析不同作者的研究成果和我们自己的结果时，我们提出了乳酸脱氢酶催化的通用模型，该模型包括正常酶 - 底物复合物、无效酶 - NAD - 丙酮酸复合物的形成以及不同效应物（包括含氮物质）的作用。
