Studies on the Mechanism of Enzyme-Catalyzed Oxidation-Reduction Reactions. VI.*Kinetic Studies with Yeast L(+)-Lactate Dehydrogenase

Biochemistry ◽  
1963 ◽  
Vol 2 (2) ◽  
pp. 209-216 ◽  
Author(s):  
J. W. Hinkson ◽  
H. R. Mahler
Keyword(s):  
Lactate Dehydrogenase ◽  
Kinetic Studies ◽  
Reduction Reactions ◽  
Oxidation Reduction ◽  
Catalyzed Oxidation

scholarly journals The lactate dehydrogenase–reduced nicotinamide–adenine dinucleotide–pyruvate complex. Kinetics of pyruvate binding and quenching of coenzyme fluorescence

1974 ◽  
Vol 139 (1) ◽  
pp. 251-259 ◽  
Author(s):  
J. Südi
Keyword(s):  
Lactate Dehydrogenase ◽  
Rate Constants ◽  
Kinetic Studies ◽  
Reduction Reaction ◽  
Reverse Direction ◽  
Total Change ◽  
Sequential Reaction ◽  
Oxidation Reduction ◽  
Dehydrogenase Reaction ◽  
Absorbing Material

The stopped-flow kinetic studies described in this and the following paper (Südi, 1974) demonstrate that a Haldane-type description of the reversible lactate dehydrogenase reaction presents an experimentally feasible task. Combined results of these two papers yield numerical values for the six rate constants defined by the following equilibrium scheme, where E represents lactate dehydrogenase: [Formula: see text] The experiments were carried out at pH8.4 at a relatively low temperature (6.3°C) with the pig heart enzyme. Identification of the above two intermediates and determination of the corresponding rate constants actually involve four series of independent observations in these studies, since (a) the reaction can be followed in both directions, and (b) both the u.v. absorption and the fluorescence of the coenzymes are altered in the reaction, and it is shown that these two spectral changes do not occur simultaneously. Kinetic observations made in the reverse direction are reported in this paper. It is demonstrated that the fluorescence of NADH can no longer be observed in the ternary complex ENADHPyr. Even though the oxidation–reduction reaction rapidly follows the formation of this complex, the numerical values of k−4 (8.33×105m−1·s−1) and k+4 (222s−1) are easily obtained from a directly observed second-order reaction step in which fluorescent but not u.v.-absorbing material is disappearing. U.v.-absorption measurements do not clearly resolve the subsequent oxidation–reduction step from the dissociation of lactate. It is shown that this must be due partly to the instrumental dead time, and partly to a low transient concentration of ENAD+Lac in the two-step sequential reaction in which the detectable disappearance of u.v.-absorbing material takes place. It is estimated that about one-tenth of the total change in u.v. absorption is due to a `burst reaction' in which ENAD+Lac is produced, and this estimation yields, from kobs.=120s−1, k−2=1200s−1.

Feedback Controlled Chemical Reactor with Feed of Two Reaction Components with Spectrophotometric Indication

1994 ◽  
Vol 59 (3) ◽  
pp. 549-557
Author(s):  
František Skopal ◽  
Václav Dušek
Keyword(s):  
Sulfuric Acid ◽  
Negative Feedback ◽  
Chemical Reactor ◽  
Reduction Reactions ◽  
Oxidation Reduction

Theoretical relationships and simplifying conditions have been derived for the feed of two reaction components into a nonisochoric reactor with ideal stirring. The feed of reaction components is controlled by the negative feedback at a constant absorbance of the reaction mixture. The theoretical relationships have been verified using model 2. order oxidation-reduction reactions of Ce(IV)/V(IV) and Fe(III)/V(III) in 1 M sulfuric acid at 20 °C.

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