Structural highlights
Publication Abstract from PubMedTyrosine phenol-lyase (TPL; E.C. 4.1.99.2) is a pyridoxal-5'-phosphate dependent enzyme that catalyzes the reversible hydrolytic cleavage of L-tyrosine to phenol and ammonium pyruvate. We have shown previously that F448A TPL has kcat and kcat/Km values for L-tyrosine reduced by about 104 (Phillips, R. S., Vita, A., Spivey, J. B., Rudloff, A. P., Driscoll, M. D., & Hay, S. (2016) ACS Catalysis, 6, 6770-6779). We have now obtained crystal structures of F448A TPL and complexes with L-alanine, L-methionine, L-phenylalanine, and 3-F-L-tyrosine at 2.05-2.27 A, as well as the complex of wild-type TPL with L-phenylalanine at 1.8 A. The small domain of F448A TPL, where Phe-448 is located, is more disordered in chain A than wild-type TPL. The complexes of F448A TPL with L-alanine and L-phenylalanine are in an open conformation in both chains, while the complex with L-methionine is a 52:48 equilibrium mixture of open and closed conformations, respectively, in chain A. Wild-type TPL with L-alanine is closed in chain A and open in chain B, and the complex with L-phenylalanine is 56:44 in open and closed conformations in chain A. Thus, the Phe-448 to alanine mutation affects the conformational equilibrium of open and closed active sites. The structure of the 3-F-L-tyrosine quinonoid complex of F448A TPL is unstrained and in an open conformation, with a hydrogen bond from the phenolic OH to Thr-124. These results support our previous conclusion that ground-state strain plays a critical role in the mechanism of TPL. Crystal Structures of Wild-type and F448A Mutant Citrobacter freundii Tyrosine Phenol-lyase Complexed with Substrate and Inhibitors: Implications for the Reaction Mechanism.,Phillips RS, Craig S Biochemistry. 2018 Sep 27. doi: 10.1021/acs.biochem.8b00724. PMID:30260636[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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