title: Enzymatic polymerization of tyrosine derivatives. Peroxidase- and protease-catalyzed synthesis of poly(tyrosine)s with different structures.
abstract: Polymerization of tyrosine derivatives has been carried out by using two enzymes, peroxidase and protease, as catalyst to give poly(tyrosine)s with different structures. Tyrosine ester hydrochlorides were oxidatively polymerized by a peroxidase in a buffer. Using a high buffer concentration produced the polymer in good yields. The resulting polymer was soluble in N,N-dimethylformamide, dimethyl sulfoxide, and methanol but was insoluble in acetone, tetrahydrofuran, and water. The ester moiety of the polymer was subjected to the alkaline hydrolysis, yielding a water-soluble polymer having the amino acid group in the side chain. The peroxidase also catalyzed the oxidative polymerization of N-acetyltyrosine to give the polymer soluble in water. The polymerization of tyrosine ester hydrochlorides proceeded in the presence of papain catalyst to give a polymer of alpha-peptide structure. The polymerization in the buffer of high phosphate concentration efficiently produced the polymer. On the other hand, the polymer formation was not observed in the low buffer concentration. The molecular weight was several thousands and almost constant during the reaction. The morphology of the precipitated polymer was examined. The product of the initial reaction stage was amorphous. After 24 h, the precipitates exhibiting clear birefringence were formed. Scanning electron microscopy observation of the polymer after 72 h showed the formation of a globular crystal in a diameter larger than 50 microm, which was not found by recrystallization of poly(tyrosine).
authors.affiliation: Department of Materials Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 606-8501, Japan.
authors.forename: Tokuma
authors.initials: T
authors.lastname: Fukuoka
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Tachibana
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Tonami
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Uyama
authors.forename: Shiro
authors.initials: S
authors.lastname: Kobayashi
mesh_terms: D001672:Biocompatible Materials / Q000138:chemical synthesis; D002384:Catalysis; D010450:Endopeptidases / Q000378:metabolism*; D008855:Microscopy, Electron, Scanning; D015394:Molecular Structure; D008970:Molecular Weight; D010455:Peptides / Q000138:chemical synthesis*; D009195:Peroxidase / Q000378:metabolism*
chemical_list: D001672:Biocompatible Materials; D010455:Peptides; C017663:polytyrosine; D009195:Peroxidase; D010450:Endopeptidases