Analysis and computer simulation of aerobic oxidation of reduced nicotinamide adenine dinucleotide catalyzed by horseradish peroxidase

Biochemistry ◽  
1977 ◽  
Vol 16 (9) ◽  
pp. 1913-1920 ◽  
Author(s):  
Kennosuke Yokota ◽  
Isao Yamazaki
Keyword(s):  
Computer Simulation ◽  
Horseradish Peroxidase ◽  
Nicotinamide Adenine Dinucleotide ◽  
Aerobic Oxidation ◽  
Nicotinamide Adenine ◽  
Reduced Nicotinamide Adenine Dinucleotide

Kinetics of the oxidation of reduced nicotinamide adenine dinucleotide by horseradish peroxidase compounds I and II

1986 ◽  
Vol 64 (4) ◽  
pp. 323-327 ◽  
Author(s):  
Mohammed A. Kashem ◽  
H. Brian Dunford
Keyword(s):  
Horseradish Peroxidase ◽  
Active Site ◽  
Nicotinamide Adenine Dinucleotide ◽  
Ph Dependence ◽  
Transient State ◽  
Nicotinamide Adenine ◽  
Compound I ◽  
Single Ionization ◽  
Reduced Nicotinamide Adenine Dinucleotide ◽  
Kinetics Of

The transient state kinetics of the oxidation of reduced nicotinamide adenine dinucleotide (NADH) by horseradish peroxidase compound I and II (HRP-I and HRP-II) was investigated as a function of pH at 25.0 °C in aqueous solutions of ionic strength 0.11 using both a stopped-flow apparatus and a conventional spectrophotometer. In agreement with studies using many other substrates, the pH dependence of the HRP-I–NADH reaction can be explained in terms of a single ionization of pKa = 4.7 ± 0.5 at the active site of HRP-I. Contrary to studies with other substrates, the pH dependence of the HRP-H–NADH reaction can be interpreted in terms of a single ionization with pKa of 4.2 ± 1.4 at the active site of HRP-II. An apparent reversibility of the HRP-II–NADH reaction was observed. Over the pH range of 4–10 the rate constant for the reaction of HRP-I with NADH varied from 2.6 × 105 to5.6 × 102 M−1 s−1 and of HRP-II with NADH varied from 4.4 × 104 to 4.1 M−1 s−1. These rate constants must be taken into consideration to explain quantitatively the oxidase reaction of horseradish peroxidase with NADH.

scholarly journals The inactivation of phenylalanine hydroxylase by 2-amino-4-hydroxy-6,7-dimethyltetrahydropteridine and the aerobic oxidation of the latter. The effects of catalase, dithiothreitol and reduced nicotinamide–adenine dinucleotide

1971 ◽  
Vol 125 (2) ◽  
pp. 563-568 ◽  
Author(s):  
A. Jakubovič ◽  
L. I. Woolf ◽  
E. Chan-Henry
Keyword(s):  
Hydrogen Peroxide ◽  
Nicotinamide Adenine Dinucleotide ◽  
Phenylalanine Hydroxylase ◽  
Liver Extract ◽  
Aerobic Oxidation ◽  
Organic Peroxide ◽  
Nicotinamide Adenine ◽  
Oxidation In Air ◽  
Reduced Nicotinamide Adenine Dinucleotide

1. Phenylalanine hydroxylase is inhibited by its cofactor, 6,7-dimethyltetrahydropterin. The rate of inactivation, which is irreversible, increases with the concentration of cofactor. 2. Catalase, in sufficient amount relative to cofactor, prevents this inactivation. More tyrosine is formed in the presence of added catalase. 3. Dithiothreitol in the presence of liver extract also prevents inactivation of the enzyme by the cofactor and stimulates hydroxylation of phenylalanine, probably by protecting the cofactor from oxidation and regenerating it from a dihydropterin reaction product. Dithiothreitol restores linearity of rate at very low enzyme concentrations. 4. Dimethyltetrahydropterin is unstable when the solution is exposed to air but is stabilized by dithiothreitol the aerobic oxidation of which is greatly accelerated by dimethyltetrahydropterin. 5. NADH together with liver extract stabilizes the cofactor but not phenylalanine hydroxylase. 6. It is suggested that either hydrogen peroxide or an organic peroxide formed by oxidation in air of the cofactor is the substance attacking phenylalanine hydroxylase, dithiothreitol and cofactor.

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