Negative Cooperativity in the Interaction of Prostaglandin H Synthase-1 with the Competitive Inhibitor Naproxen Can Be Described as the Interaction of a Non-competitive Inhibitor with Heterogeneous Enzyme Preparation.

The kinetic mechanism of the interaction of nonsteroidal anti-inflammatory drugs (NSAIDs) with their main pharmacological target, prostaglandin H synthase (PGHS), has not yet been established. We showed that inhibition of PGHS-1 from sheep vesicular glands by naproxen (a representative of NSAIDs) demonstrates a non-competitive character with respect to arachidonic acid and cannot be described within a framework of the commonly used kinetic schemes. However, it can be described by taking into account the negative cooperativity of naproxen binding to the cyclooxygenase active sites of the PGHS-1 homodimer (the first naproxen molecule forms a more stable complex (K = 0.

Prostaglandin H synthase kinetics in the two-phase aqueous-micellar system.

Reaction mixture for PGHS (prostaglandin-H-synthase) is a two-phase system including micellar hydrophobic phase and hydrophilic aqueous phase. Reagents added to the mixture are distributed between phases, thus concentrations of reagents dissolved in phases can differ significantly from their overall contents. Using dynamic light scattering we found that the hydrophobic phase produced by tween-20 consists of micelles, which radius (4-5nm) does not depend on either tween-20 overall content (0.

[Bactericidal action of non-thermal plasma on biofilms formed in vitro and within a root channel].

Aim: Evaluation of efficiency of non-thermal plasma as bactericidal agent affecting biofilms formed in vitro and on walls of a root channel.

Materials And Methods: The multiple antibiotic resistant strain Staphylococcus epidermidis isolated from pulpitis was used. Biofilms formed in vitro on the plastic surface and ex vivo at the walls of the root canal were treated with plasma torch formed by argon:air (9:1) mixture eradiated with 100 kHz electrtomagnetic field.

[Effect of cold plasma on the E. coli cell wall and plasma membrane].

The effect of cold plasma on E. coli cells was studied. It was shown that the treatment of E.

Inhibition of cyclooxygenase activity of prostaglandin-H-synthase by excess substrate (molecular oxygen).

For the cyclooxygenase reaction of prostaglandin-H-synthase isolated from ram vesicular glands, dependences of the initial reaction rate, the maximal yield of the product, and the rate constant of enzyme inactivation in the course of reaction on oxygen concentration were studied in the absence and in the presence of electron donor in the reaction medium. It is shown that in the absence of electron donor the cyclooxygenase reaction is strictly governed by Michaelis-Menten kinetics over a wide range of oxygen concentrations (5-800 µM). In the presence of electron donor in the reaction medium it was found that cyclooxygenase reaction is inhibited by an excess of dissolved oxygen: the maximal values of the initial reaction rate and yield of the product are attained at oxygen concentration 50 µM, and its increase to 500 µM causes twofold decrease in the initial rate and maximal yield.