NAD-dependent substrates oxidation

Tables and figures present means and their standard deviations (M + m). In Figures 2 and, correlations between unsaturation coefficients of C 18 and C 20 fatty acids and the rates of NAD-dependent substrate oxidation are presented they were calculated using Statistica v. 6 software for Windows.

The observed alterations possibly inOience lipid-protein relation and thns alter the activity of the enzymes associated with the membrane. Indeed, IW lesnlts in a decrease of the maximal rates of NAD-dependent substrates oxidation. The rate of the pair glutamate + malate oxidation in the presence of uncoupling agent (FCCP) drops from 70.0 4.6 down to 48.9 3.2 ng oxygen atom/mg of protein min and the respiratory control rate (RCR) decreases from 2.27 0.1 to 1.7 0.2 (Table 2). 

TABLE 2 Effects of IW and MF on the rate of NAD-dependent substrate oxidation by mitochondria isolated from pea seedlings, ng-atom/(mg protein min). 

FIG LIRE 2 Correlation between the unsaturation coefficient of C20 fatly acids and maximum rates of NAD-dependent substrate oxidation. Y-axis shows the maximum rates of NAD-dependent substrate oxidation X-axis- unsaturation coefficient of Cl 8 fatty acids. 

NAD-dependent substrate oxidation. At the same time, mitoehondria of storage organs and seeds ate eharaeterized by relatively low rates of oxidation of NAD-dependent substrates. The result of maintenance high activity of NAD-dependent dehydrogenases is the support the energy processes in cell that promotes the resistance of plant to varying envirorunental conditions. Under conditions of IW, protective effect of MF is apparently determined by maintenance in the content of unsaturated fatly acids with 18 and 20 carbon atoms in lipid phase of mitochondrial membranes. 

Under conditions of AHH, there was observed a decrease in the highest rates of NAD-dependent substrate oxidation the rates of malate +glu-tamate oxidation in the presence of ADP or uncoupler (FCCP) were by 24.3-30% lower than in control mitochondria (Table 1). 

TABLE 1 The effect of hypobaric hypoxia, potassium phenosan, and anphen on rates of oxidation of NAD-dependent substrates (Oxidation rates are expressed in ng moles of Oj mg.protein min, number of experiments is 10). 

The insufficient watering resulted in a decrease in the maximum rates of oxidation of NAD-dependent substrates (Table 3). 

Nearly all NAD+-dependent dehydrogenases studied follow an ordered bisubstrate mechanism. In this mechanism, the oxidation of a substrate proceeds in a sequential manner first, NAD+ binds in the active site of the dehydrogenase then the substrate binds next a hydride equivalent is transferred in a chemical step from the bound substrate to the bound NAD+, hence, oxidising the substrate and reducing the NAD+ to NADH the oxidised substrate is then released from the active site and is finally followed by the NADH. 

A general method has been developed for utilization of cofactor-requiring enzymes in organic media [139]. ADH from horse liver as well as NADH were attached onto the surface of glass beads and afterwards suspended in a water-immiscible organic solvent containing the substrate. This method can be applied to other NAD+-dependent enzymes as well. Both NADH and NAD+ are efficiently regenerated with ADH-catalyzed oxidation of ethanol and reduction of isobutyr-aldehyde, respectively (Fig. 31). 

Consider the NAD -dependent enzyme dehydrogenase, which catalyzes the oxidation of a substrate, RH ... 

Figure 6 The most common paradigm for hemoprotein-catalyzed substrate oxidation involves heterolytic scission of the 0-0 bond of an iron-bound peroxo species to give an Fe(IV) = O ferryl intermediate and either a porphyrin radical or a protein radical. The peroxo intermediate is generated in the cytochromes P450 by in situ NAD(P)H-dependent reduction of O2, and in the peroxidases by reaction with H2O2.

Diverse soluble enzymes, called aldo-keto reductases. cany out bioreduction of aldehydes and ketones. They are found in the liver and other tissues (e.g.. kidney). As a general class, these soluble en7.ynie.s have similar physi-ochemical properties and broad substrate specificities and require NADW as a cofactor. Oxidoreductase enzymes that catty out both oxidation and reduction reactions also can reduce aldehydes and ketones. " For example. Ihe important liver alcohol dehydrogenase is an NAD -dependent oxido-icductase that oxidizes ethanol and other aliphatic alcohols to aldehydes and ketones. In the presence of NADH or... 

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