Biochem. J. (2003) 373
(733–738) (Printed in Great Britain)
X-ray structure of a putative reaction intermediate of 5-aminolaevulinic acid dehydratase
Peter T. ERSKINE*, Leighton COATES*, Danica BUTLER*, James H. YOUELL*, Amanda A. BRINDLEY†, Steve P. WOOD*, Martin J. WARREN†, Peter M. SHOOLINGIN-JORDAN* and Jonathan B. COOPER*1
*Division of Biochemistry and Molecular Biology, School of Biological Sciences, University of Southampton, Bassett Crescent East, Southampton, SO16 7PX, U.K., and †School of Biological Sciences, Queen Mary, Mile End Road, London, E1 4NS, U.K.
The X-ray structure of yeast 5-aminolaevulinic acid dehydratase, in which the catalytic site of the enzyme is complexed with a putative cyclic intermediate composed of both substrate moieties, has been solved at 0.16 nm (1.6 Å) resolution. The cyclic intermediate is bound covalently to Lys263 with the amino group of the aminomethyl side chain ligated to the active-site zinc ion in a position normally occupied by a catalytic hydroxide ion. The cyclic intermediate is catalytically competent, as shown by its turnover in the presence of added substrate to form porphobilinogen. The findings, combined with those of previous studies, are consistent with a catalytic mechanism in which the C–C bond linking both substrates in the intermediate is formed before the C–N bond.
Key words: 5-aminolaevulinic acid dehydratase, catalytic mechanism, reaction intermediate, trapped intermediate, X-ray structure.
Abbreviations used: ALA, 5-aminolaevulinic acid; ALAD, 5-aminolaevulinic acid dehydratase; PBG, porphobilinogen; TLS, translation-libration-screw.
1To whom correspondence should be addressed (e-mail J.B.Cooper@soton.ac.uk).
Received 4 April 2003; accepted 2 June 2003
Published as BJ Immediate Publication 2 June 2003, DOI 10.1042/BJ20030513
The Biochemical Society, London ©2003
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