| Summary: | 碩士 === 國立中興大學 === 生命科學院碩士在職專班 === 100 === The peptidylarginine deminase (PAD) family is a kind of post-translational modifying enzyme that can catalyes protein citrullination (deimination) which is the conversion of protein-bound arginine to citrulline (Arg -> Cit). PAD4, one of the PAD isoform family, which is a dimeric enzyme catalyes protein in the presence of calcium. PAD4 is considered as the important enzyme for rheumatoid arthritis in the past few years. According to the research, PAD4 will initiate immunity of this disease. PAD4 recently has been found to overexpress in many cancers and malignant tissues that closely related to the apoptosis and cell cycle arrest. In order to explore the PAD4 between the role of the enzyme and disease-related role, we have purified a variety of disease-related protein to measure PAD4 enzyme activity by enzyme kinetics assay. The results showed that PAD4 can use antizyme (AZ) as the protein substrate and the kinetic data showed that R42, R81, R86, R100, R188 and R199 are critical residues to be citrullinated in AZ. For this reason, we suggested that AZ may be as a substrate for PAD4. However, AZ mainly combinated with human ornithine decarboxylase (hODC) to regulate the concentrations of polyamine in cells. Our data showed that incubation of AZ with PAD4 and multisite mutations will reduce the ability to inhibit ODC activity. Therefore, we could know that PAD4 may change AZ founction after AZ citrullination. By according to these results, we propose that PAD4 may play an important role in the regulation of AZ of ODC activity.
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