Neuronal Nitric Oxide Synthase:  Substrate and Solvent Kinetic Isotope Effects on the Steady-State Kinetic Parameters for the Reduction of 2,6-Dichloroindophenol and Cytochromec3+ †

Biochemistry ◽  
2002 ◽  
Vol 41 (1) ◽  
pp. 196-204 ◽  
Author(s):  
Kirsten R. Wolthers ◽  
Michael I. Schimerlik
Keyword(s):  
Nitric Oxide ◽  
Steady State ◽  
Nitric Oxide Synthase ◽  
Isotope Effects ◽  
Neuronal Nitric Oxide Synthase ◽  
Kinetic Isotope Effects ◽  
Kinetic Isotope ◽  
Steady State Kinetic ◽  
Oxide Synthase ◽  
State Kinetic

scholarly journals The mechanism of action of β-galactosidase. Effect of aglycone nature and α-deuterium substitution on the hydrolysis of aryl galactosides

1973 ◽  
Vol 133 (1) ◽  
pp. 89-98 ◽  
Author(s):  
Michael L. Sinnott ◽  
Ian J. L. Souchard
Keyword(s):  
Steady State ◽  
Isotope Effects ◽  
Ion Pair ◽  
Enzyme Mechanism ◽  
Kinetic Isotope ◽  
Deuterium Substitution ◽  
Steady State Kinetic ◽  
Hydrolysis Of ◽  
State Kinetic ◽  
Step Mechanism

1. Steady-state kinetic parameters for the β-galactosidase-catalysed hydrolysis of 13 aryl β-d-galactopyranosides show no simple dependence on aglycone acidity. 2. α-Deuterium kinetic isotope effects (kH/kD) for seven of these substrates, measured under steady-state conditions with [S]»Km, vary from 1.00 for poor substrates to 1.25 for hydrolysis of the galactosyl-enzyme. 3. Methanolysis of the galactosyl-enzyme in 1.5m-methanol increases KH/kD for degalactosylation, but leaves that for hydrolysis of ‘slow’ substrates unchanged. 4. These data are incompatible with a simple two-step mechanism. A scheme consisting of a conformation change, liberation of a galactopyranosyl cation in an intimate ion-pair, non-productive but preferential collapse of the ion-pair to a covalent species and reaction of the galactosyl enzyme through the ion-paired form is proposed. 5. This scheme is used to rationalize previously puzzling data about the enzyme mechanism.

Role of neuronal nitric oxide synthase in gastric hypermotility induced by intracisternal TRH analog, RX 77368, in anesthetized rats

2001 ◽  
Vol 120 (5) ◽  
pp. A533-A534
Author(s):  
K KANAMOTO ◽  
K KAWAKUBO ◽  
D ADELSON ◽  
Y TACHE
Keyword(s):  
Nitric Oxide ◽  
Nitric Oxide Synthase ◽  
Neuronal Nitric Oxide Synthase ◽  
Anesthetized Rats ◽  
Oxide Synthase
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