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The Structure of Y71F Tyrosine Phenol-lyase from Citrobacter freundii Complexed with 3-Fluoro-L-tyrosine

Tyrosine phenol-lyase (TPL), a homotetrameric pyridoxal 5'-phosphate (PLP)-dependent enzyme, catalyses the beta-elimination of L-tyrosine, i.e. the reversible hydrolytic cleavage of L-tyrosine to phenol and ammonium pyruvate [1]. In vitro TPL can also catalyse some other reactions e.g. the synthesis of 3, 4-dihydroxy- L-phenylalanine (L-DOPA) from catechol, pyruvate and ammonia [2]). The beta-elimination proceeds via several intermediatesand mechanistically it is a very interesting reaction [1]. In order to reveal certain details in the enzyme reaction mechanism, the X-ray structure of the Y71F mutant of Citrobacter freundii TPL complexed with the substrate analogue 3-fluoro-L-tyrosine has been determined at 2 A resolution. There are two active sites in asymmetric unit: one in the "closed" and the other one in the "open" conformation. Both active sites are occupied by the ligand in the quinonoid form but with slightly different geometries due to the different active sites conformations. The catalytic roles of certain active site residues have been structurally confirmed. It is assumed that the active site transition from the "open" to the "closed" form during the enzyme reaction is important for the enzyme catalytic efficiency. 1. R. S. Phillips, T. V. Demidkina & N. G. Faleev, Biochim. Biophys. Acta 1647 (2003) 167-172. 2. S.-G. Lee, S.-P. Hong & M.-H. Sung, Enzyme Microb. Technol. 25 (1999) 298-302.

tyrosine phenol-lyase; pyridoxal 5'-phosphate; L-tyrosine; 3-fluoro-L-tyrosine; quinonoid intermediate; protein crystallography

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