INTRACELLULAR DISTRIBUTION AND SOME PROPERTIES OF HEXOKINASE OF BOVINE ADRENAL MEDULLA

1966 ◽  
Vol 44 (6) ◽  
pp. 879-891 ◽  
Author(s):  
C. J. Toews
Keyword(s):  
Adenosine Triphosphate ◽  
Adrenal Medulla ◽  
Initial Velocity ◽  
Adenosine Diphosphate ◽  
Product Inhibition ◽  
Intracellular Distribution ◽  
Velocity Analysis ◽  
Bovine Adrenal Medulla ◽  
Sequential Mechanism ◽  
Ordered Sequential Mechanism

The intracellular distribution of the hexokinase of the adrenal medulla was studied. Most of the hexokinase was found, in about equal amounts, in the mitochondria and the nonparticulate cytoplasm. The amount of hexokinase associated with the mitochondria was shown to be dependent on the hexokinase concentration in the medium surrounding the mitochondria.The hexokinase of the adrenal medulla was shown to be noncompetitively inhibited by adenosine diphosphate (ADP) with respect to glucose and adenosine triphosphate (ATP). It was competitively inhibited with respect to glucose by mannose, fructose, and galactose. Glucose-6-phosphate (0.09 M) did not inhibit the hexokinase. The data on product inhibition and initial velocity analysis support the concept of an ordered sequential mechanism for adrenal-medulla hexokinase.

scholarly journals Kinetic studies with skeletal-muscle hexokinase

1966 ◽  
Vol 100 (3) ◽  
pp. 739-744 ◽  
Author(s):  
CJ Toews
Keyword(s):  
Skeletal Muscle ◽  
Initial Velocity ◽  
Gel Filtration ◽  
Kinetic Studies ◽  
Competitive Inhibitor ◽  
Product Inhibition ◽  
Velocity Analysis ◽  
Sequential Mechanism ◽  
Ammonium Sulphate Fractionation ◽  
Ordered Sequential Mechanism

Rat skeletal-muscle hexokinase was partially purified by ammonium sulphate fractionation and gel filtration. The mechanism of the skeletal-muscle hexokinase was studied kinetically by initial-velocity analysis and product inhibition. Glucose 6-phosphate was a non-competitive inhibitor of glucose and ATP. ADP was a non-competitive inhibitor of glucose and a competitive inhibitor of ATP. The data on product inhibition and initial-velocity analysis of skeletal-muscle hexokinase support an ordered sequential mechanism (ordered Bi Bi) where the addition of substrates and release of products is in the order: ATP, glucose, glucose 6-phosphate and ADP.

scholarly journals Kinetic studies with the low-Km aldehyde reductase from ox brain

1985 ◽  
Vol 227 (2) ◽  
pp. 621-627 ◽  
Author(s):  
C M Ryle ◽  
K F Tipton
Keyword(s):  
Initial Velocity ◽  
Initial Rate ◽  
Kinetic Studies ◽  
Product Inhibition ◽  
Binary Complex ◽  
Aldehyde Reductase ◽  
Apparent Dissociation Constant ◽  
Displacement Mechanism ◽  
Sequential Mechanism ◽  
Inhibition Studies

Initial-rate studies of the low-Km aldehyde reductase-catalysed reduction of pyridine-3-aldehyde by NADPH gave families of parallel double-reciprocal plots, consistent with a double-displacement mechanism being obeyed. Studies on the variation of the initial velocity with the concentration of a mixture of the two substrates were also consistent with a double-displacement mechanism. In contrast, the initial-rate data indicated that a sequential mechanism was followed when NADH was used as the coenzyme. Product-inhibition studies, however, indicated that a compulsory-order mechanism was followed in which NADPH bound before pyridine-3-aldehyde with a ternary complex being formed and the release of pyrid-3-ylcarbinol before NADP+. The apparently parallel double-reciprocal plots obtained in the initial-rate studies with NADPH and pyridine-3-aldehyde were thus attributed to the apparent dissociation constant for the binary complex between the enzyme and coenzyme being finite but very low.

scholarly journals The kinetics and reaction mechanism of the nicotinamide–adenine dinucleotide phosphate-specific glycerol dehydrogenase of rat skeletal muscle

1967 ◽  
Vol 105 (3) ◽  
pp. 1067-1073 ◽  
Author(s):  
C. J. Toews
Keyword(s):  
Skeletal Muscle ◽  
Reaction Mechanism ◽  
Nicotinamide Adenine Dinucleotide ◽  
Initial Velocity ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Product Inhibition ◽  
Glycerol Dehydrogenase ◽  
Velocity Analysis ◽  
Rat Skeletal Muscle ◽  
Ammonium Sulphate Fractionation

The NADP-specific glycerol dehydrogenase of rat skeletal muscle has been partially purified by ammonium sulphate fractionation. The enzyme has been studied kinetically by initial-velocity analysis, product inhibition and inhibition by fluoride. The experimental results indicate that the reaction mechanism for the enzyme is ordered such that the first product leaves the enzyme before the addition of the second substrate.

Soluble serotonin and catecholamine binding proteins in the bovine adrenal medulla

1993 ◽  
Vol 23 (4) ◽  
pp. 343-350 ◽  
Author(s):  
Jef Pinxteren ◽  
Marlene Jimenez Del Rio ◽  
Carlos Velez Pardo ◽  
Guy Ebinger ◽  
Georges Vauquelin ◽  
...  
Keyword(s):  
Adrenal Medulla ◽  
Binding Proteins ◽  
Bovine Adrenal Medulla
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