Studies Of Mimics Of Peroxidase

Objection: Peroxidases, which exist in the animals, plants and aerobicmicroorganism, cooperate with other antioxidants to balance the metabolizationof free radicals. In despite of the significance of the peroxidases in the preventionand therapy of the diseases caused by the free radicals, the disadvantages of thenatural peroxidases make it necessary to design and synthesize effective enzymemimics. According to the structure of the enzyme mimics, they could beclassified as simple organic compounds, peptide mimics and protein mimics.Compared to the simple organic compounds, the peptide mimics have theadvantages of low toxicity, high activity and easy synthesis. At the same time,compared with the protein mimics, the peptide mimics have the low molecularweight and high stability. Also the modern technology makes it possible tosynthesize peptide of any sequences.Methods:In this thesis, the phage displaypeptide library was used to screen the small peptide ligand of deuterohemin, andthen the peptide mimic of peroxidases, which use the hemin as the prostheticgroup, was carried out. Because of the low solubility of the deuterohemin, theDeuterohemin-His-Peptide-6 (Dh-AHTVEK) was taken as the screening target.In the mean time, according to the peptide sequence of the DhHP-6, a peptidewas synthesized in the manual way in order to reduce the effect of theintroduction of the peptide to the deuterohemin. After three rounds of screening,individual clones were isolated and sequenced, and a series of small peptideligands specifical to the deuterohemin were obtained. One sequence with highoccurrence frequency has the conserved domain His/Trp/Arg of natural ascorbateperoxidase. From result of the sequence alignment in the database, this smallpeptide sequence is homologous to many catalase, but no uniform sequence existsin the database. This indicates that the putative peptide mimic has the potential ofbecoming a new mimic of peroxidase. On the basis of the data and informationobtained from the experiment, several deuterohemin-His-peptides were designed.In the mimics, the deuterohemin take the place of the hemin whose alkenyls areeasiliy oxidized by the peroxide, which reduces its stability to the peroxide. Thenone mimic of peroxidase, Dh-β -Ala-Phe-His-Trp-Lys-Pro-Tyr-Arg wassynthesized.Conclusions: the mimic of peroxidase was was measured, and have arelative high enzyme activity.