Naslov
Structural basis for the catalytic activity of tyrosine phenol-lyase

Autori
Milić, Dalibor ; Demidkina, Tatyana V. ; Matković-Čalogović, Dubravka ; Antson, Alfred A.

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
International School of Crystallography, 42nd Course, Structure and Function from Macromolecular Crystallography: Organisation in Space and Time - Programme, Lecture Notes & Poster Abstracts / - , 2010, 206-206

Skup
International School of Crystallography, 42nd Course, Structure and Function from Macromolecular Crystallography: Organisation in Space and Time

Mjesto i datum
Erice, Italija, 03.06.2010. - 13.06.2010

Vrsta sudjelovanja
Poster

Vrsta recenzije
Nije recenziran

Ključne riječi
beta-elimination; enzyme; protein crystallography; pyridoxal 5'-phosphate; quinonoid; reaction mechanism; tyrosine phenol-lyase

Sažetak
Tyrosine phenol-lyase (TPL) is a pyridoxal-5'-phosphate (PLP)-dependent enzyme which catalyzes the reversible hydrolytic β-elimination reaction of L-tyrosine to produce phenol and ammonium pyruvate. In vitro, TPL also catalyzes some other reactions with different substrates. It is a homotetrameric protein with the active sites (one per subunit) located at the interface of two subunits forming the catalytic dimer [1]. Each protein subunit, and the corresponding active site, can adopt two different conformations: open and closed [2, 3]. The postulated mechanism of the physiological β-elimination reaction [4] includes several key steps: (a) formation of the external aldimine in the reaction of the internal aldimine with the substrate ; (b) Cα proton abstraction performed by the cofactor-binding residue Lys257 and resulting in formation of the quinonoid intermediate ; (c) Cγ protonation by Tyr71 assisted by Arg381 ; and, finally, (d) cleavage of the Cβ–Cγ bond to form phenol and the α-aminoacrylate intermediate which is decomposed to ammonium pyruvate. We have solved crystal structures of several complexes with substrate analogs. These structures mimic the reaction intermediates and suggest that closure of the active site is crucial for abstraction of phenol during the -elimination of L-tyrosine. The closure protects the key quinonoid intermediate from the solvent and brings the catalytically important residues Arg381, Thr124, and Phe448 into positions suitable for interaction with the substrate. 1. Antson, A. A., Demidkina, T. V., Gollnick, P., Dauter, Z., Von Tersch, R. L., Long, J., Berezhnoy, S. N., Phillips, R. S., Harutyunyan, E. H., and Wilson, K. S. (1993) Biochemistry 32, 4195–4206. 2. Milić, D., Matković-Čalogović, D., Demidkina, T. V., Kulikova, V. V., Sinitzina, N. I., and Antson, A. A. (2006) Biochemistry 45, 7544–7552. 3. Milić, D., Demidkina, T. V., Faleev, N. G., Matković-Čalogović, D., and Antson, A. A. (2008) J. Biol. Chem. 283, 29206–29214. 4. Phillips, R. S., Demidkina, T. V., and Faleev, N. G. (2003) Biochim. Biophys. Acta 1647, 167–172.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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