Properties of chemically oxidized kininogens

Area of Science:

• Biochemistry
• Molecular Biology
• Inflammation Research

Background:

• Kininogens are multifunctional proteins regulating kinin formation, coagulation, and fibrinolysis.
• Reactive oxygen species (ROS) are released during inflammation and can modify proteins.

Purpose of the Study:

• To investigate how oxidation of methionine residues in human kininogens affects their function.
• To determine the impact of oxidation on kinin release and kallikrein binding.

Main Methods:

• Oxidation of high (HK) and low (LK) molecular mass kininogens using N-chlorosuccinimide (NCS) and chloramine-T (CT).
• Amino acid analysis to confirm methionine oxidation to methionine sulfoxide.
• Assays to measure kinin production by plasma and tissue kallikreins.
• Assessment of (pre)kallikrein binding to oxidized kininogens.
• Papain inhibition assays to evaluate cysteine proteinase inhibitory activity.

Main Results:

• Oxidation resulted in nearly complete conversion of methionine to methionine sulfoxide.
• Kinin production by kallikreins from oxidized kininogens was reduced by at least 70%.
• NCS-oxidized HK showed virtually no kinin formation and impaired (pre)kallikrein binding.
• Oxidation did not significantly affect the inhibitory activity of kininogens against papain.

Conclusions:

• Methionine oxidation, particularly at Met-361, significantly reduces kinin release from kininogens.
• Oxidation can cause structural changes affecting (pre)kallikrein binding, further impairing kinin formation.
• The inhibitory function of kininogens against cysteine proteinases remains largely unaffected by oxidation.