| NADH is a kind of necessary coenzyme in cellular energy metabolism, which is indispensable to all kinds of activity of life phenomenon, cellular renewal, structure maintaining and balance of life. In addition, NADH plays a significant role in the process such as glycolysis, citric acid cycle and photosynthesis of transfer electron. During electron transport, electrons enter the chain by transfer from NADH and exit by transfer to oxygen. The oxidation of NADH in the electron-transport chain releases energy, much of which is captured by mitochondrial ATP-synthesizing system. Multienzyme redox system is the most important biological oxidation process in cellular respiration chain. It is widely employed in metabolism of glucose, fat and protein to play a central functional role for dehydrogenation. Through this system, oxygen demanded by cellular is almost combined with hydrogen from metabolite to form water. In addition, it has been shown by numerous studies that cellular redox state especially NAD+/NADH ratio (NAD level) may be a primary control site in numerous biological process linked to rhythm, senescence, cancer and death. NADH not only is an import biochemical regent, but also acts as a pharmaceutical product for protecting cellular. The function of coenzyme NADH is to increase the level of energy metabolism, to repair cellular damage, to improve cellular stress ability, and decrease cytotoxicity of chemotherapy drugs and radiation against normal tissue. NADH is a metabolic regulator of transcription, longevity and disease. NADH stimulates tyrosine hydroxylase and dopamine biosynthesis, and is effective in the Treatment of Parkinson's Disease. There are several nutrients available that stimulate brain function. NADH is one that has been recently introduced to the health market. Therefore, dynamical measurement of the cellular NAD+/NADH redox state in real time is a significant study to develop an understanding of metabolic regulation in intact cell.The development of life-science provides new challenge and opportunity for chemistry. The life phenomenon could be well explained by the chemical theory and method. Enzyme analytical kinetic methods have been extensively used inseveral areas of analytical chemistry such as in clinical, pharmaceutical, agricultural, industrial applications and process monitoring. The rate of an enzyme-catalyzed reaction can be affected by a number of factors: enzyme and substrate concentration, pH, characteristics of the substrate, temperature and the presence of cofactors, inhibitor and activator. In this paper we analyze inhibitory effect and discuss its physiological importance. The study of enzyme inhibition has a significant role in knowing active site and reactive site of enzyme, and understanding of specificity and mechanisms by which enzymes and toxic agents work. Also, it is important in regulating NAD level and retarding cellular senescence.In this work, biological redox systems related to life and health are studied by using fluorescence spectra and kinetic spectra. This work could be divided into two main parts; those are inhibitory effect on multienzyme redox system, and determination of the intracellular NAD level. A new idea is proposed to regulate intracellular NAD level by studying inhibitory effect of bio-active substances on multienzyme redox systems. Through kinetic methods, enzyme inhibition is studied and mechanisms by which enzymes work are discussed. Furthermore, new quantitative methods for bio-active substances are established.The main contents of this study could be described as follows:1. Inhibitory effect of captopril on H2O2-NADH-Hb system is studied by 3D fluorescent spectra. Captopril is proposed as an electron transport inhibitor to regulate NAD level. This method not only develops a new idea to inhibit electron transport in process of respiratory chain by captopril, but also establishes a new fluorimetric method based on competitive inhibitory effect of captopril on the multienzyme redox system with Hb as catalyst. The method is very simple...
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