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B6db references: 22050617

type Journal Article
authors Phillips, R. S.; Demidkina, T. V.; Zakomirdina, L. N.; Bruno, S.; Ronda, L.; Mozzarelli, A.
title Crystals of tryptophan indole-lyase and tyrosine phenol-lyase form stable quinonoid complexes
journal J Biol Chem
ui 22050617
year (2002)
volume 277
number 24
pages 21592-7.
keywords Catalysis
abstract The binding of substrates and inhibitors to wild-type Proteus vulgaris tryptophan indole-lyase and to wild type and Y71F Citrobacter freundii tyrosine phenol-lyase was investigated in the crystalline state by polarized absorption microspectrophotometry. Oxindolyl-lalanine binds to tryptophan indole-lyase crystals to accumulate predominantly a stable quinonoid intermediate absorbing at 502 nm with a dissociation constant of 35 microm, approximately 10-fold higher than that in solution. l-Trp or l-Ser react with tryptophan indole-lyase crystals to give, as in solution, a mixture of external aldimine and quinonoid intermediates and gem-diamine and external aldimine intermediates, respectively. Different from previous solution studies (Phillips, R. S., Sundararju, B., & Faleev, N. G. (2000) J. Am. Chem. Soc. 122, 1008- 1114), the reaction of benzimidazole and l-Trp or l-Ser with tryptophan indole-lyase crystals does not result in the formation of an alpha- aminoacrylate intermediate, suggesting that the crystal lattice might prevent a ligand-induced conformational change associated with this catalytic step. Wild-type tyrosine phenol-lyase crystals bind l-Met and l-Phe to form mixtures of external aldimine and quinonoid intermediates as in solution. A stable quinonoid intermediate with lambda(max) at 502 nm is accumulated in the reaction of crystals of Y71F tyrosine phenol- lyase, an inactive mutant, with 3-F-l-Tyr with a dissociation constant of 1 mm, approximately 10-fold higher than that in solution. The stability exhibited by the quinonoid intermediates formed both by wild- type tryptophan indole-lyase and by wild type and Y71F tyrosine phenol- lyase crystals demonstrates that they are suitable for structural determination by x-ray crystallography, thus allowing the elucidation of a key species of pyridoxal 5'-phosphate-dependent enzyme catalysis.
last changed 2002/11/12 16:17

B6db references