Сharacteristics of Glutathione Peroxidase of Spermatozoa of Infertile Men
Keywords:glutathione peroxidase, antioxidant system, male infertility, pathospermia
It is well known that the unbalancing between the intensity of lipoperoxidation processes and the activity of antioxidant defense systems leads to the development of oxidative stress, which is a potential prerequisite for the development of sperm dysfunction. A special role in the system of antioxidant protection belongs to the glutathione system, in particular glutathione peroxidise, which inactivates the active forms of Oxygen with the simultaneous oxidation of reduced glutathione. The aim of present work is to study the kinetic properties of glutathione peroxidise of spermatozoa in fertile and infertile men with different forms of pathospermia.
The activity of glutathione peroxidise was determined by the amount of reduced glutathione (GSH) that was used to neutralize hydrogen peroxide in the glutathione peroxidase reaction. The apparent kinetic parameters characterizing the glutathione peroxidise reaction - the apparent affinity constant for GSH and the maximum reaction rate were determined in the Lineweaver–Burk plot (or double reciprocal plot).
It was found that increasing the concentration of GSH in the incubation medium leads to a gradual increase in enzymatic activity of glutathione peroxidise reaching the plateau. The maximum activity of glutathione peroxidise of sperm cells in fertile and infertility men was noted in the presence of 5 mM GSH in the incubation medium. The value of maximum reaction rate for glutathione peroxidise of infertility men with different forms of pathospermia was 2,4–4,1 fold lower compared to this value in fertile men with normosospermia. At the same time, there was no statistically significant difference in maximum reaction rate between different forms of pathospermia. The value of the apparent affinity constant for GSH in the spermatozoa of the infertility men was 1,9–4,9 fold higher that of the spermatozoa of the normozoospermic males, indicating a decrease in the enzyme affinity for GSH in the pathospermia.
In interpreting the obtained kinetic parameters determined by GSH, it has been shown that in the pathospermia the inhibition of glutathione peroxidise occurs in a mixed type-both by reducing the reaction rate of the enzyme and by reducing the affinity constant to the substrate.
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