Protein C inhibitor is a serine protease inhibitor that limits the activity of protein C. An N-terminal fragment of PCI is a possible serum biomarker for prostate cancer. Protein C inhibitor is activated by heparin against thrombin. Protein C inhibitor is serine protease inhibitor of serpin type that is found in most tissues and fluids, including blood plasma, seminal plasma and urine of human. It is a 52kD glycoprotein and belongs toserine protease inhibitor super family of protein. In the beginning protein C Inhibitor was identified as an inhibitor of activated protein C, it is currently clear that this inhibitor has an expansive specificity, inhibiting several blood coagulation enzymes counting thrombin and factor Xa.
Isolation
In the beginning, protein C inhibitor was originally identified in human plasma by Griffin and Marlar and first isolation was performed by Suzuki et al. Protein C inhibitor can be isolated from human plasma using an ordinary chromatographic procedure consisting of barium citrate adsorption, polyethylene glycol fractionation, DEAE-Sepharose CL-6B treatment, ammonium sulfate fractionation, dextran sulfate-agarose chromatography, gel filtration on ACA-44, and DEAE-Sephacel chromatography.
The in vivohalf timedegradation of protein C inhibitor in plasma is found to be 23 hours, whereas the half time degradation of protein C inhibitor and protein C complex is 20 minutes.
Binding with heparin
Protein C inhibitors have ability to inhibit protein C, thrombin and other enzymes that are stimulated by heparin. The heparin binding site of protein C inhibitor is from 264-283 region. Heparin enhances the rate of inhibition leading to the conformational change in the structure of Protein C and other proteases. The binding site of heparin is different for protein C inhibitor and other proteases Heparin regulates the protein C inhibitor activity and furthermore its specificity in those system where there is presence of two or more target proteases.
Clinical significance
As an antimicrobial agent
Protein C inhibitor interacts with lipid membrane subsequently leading to permeabilization of bacterial pathogen exerting the antimicrobial activity. Protein C inhibitor a potent antimicrobial agent that have ability to destroy the bacterial cell wall, causing death of the bacteria.
Reproduction
Protein C inhibitor significantly reduces fertilization by inhibiting both the binding and penetration of zona free hamster oocytes by human sperm. This effect of PCI is dose dependent as 0.04MicroM PCI inhibited 50% binding and penetration ability.
Inhibition of tumor growth
PCI communicated by malignant cells smothers tumor invasion by hindering urokinase-sort plasminogen activator, and restrains tumor development and metastasis which is independent of its protease inhibitory activity.
Deficiency
Deficiency of protein C inhibitor in the human body may cause male infertility. Protein C inhibitor has a role in reproduction as it has ability to inhibit the sperm protease acrosin. Large amounts of protein C inhibitor circulate in the male reproductive organ as a plasma protein. Either deficiency or the presence of inactive protein C inhibitor can lead to male caused infertility.
