2hj4
Crystal structure of Alcaligenes faecalis AADH complex with p-nitrobenzylamine
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OverviewOverview
Structure-activity correlations have been employed previously in the, mechanistic interpretation of TTQ-dependent amine dehydrogenases using a, series of para-substituted benzylamines. However, by combining the use of, kinetic isotope effects (KIEs) and crystallographic analysis, in, conjunction with structure-reactivity correlation studies, we show that, para-substituted benzylamines are poor reactivity probes for TTQ-dependent, aromatic amine dehydrogenase (AADH). Stopped-flow kinetic studies of the, reductive half-reaction, with para-substituted benzylamines and their, dideuterated counterparts, demonstrate that C-H or C-D bond breakage is, not fully rate limiting (KIEs approximately unity). Contrary to previous, reports, Hammett plots exhibit a poor correlation of structure-reactivity, data with electronic substituent effects for para-substituted benzylamines, and phenylethylamines. Crystallographic studies of enzyme-substrate, complexes reveal that the observed structure-reactivity correlations are, not attributed to distinct binding modes for para-substituted benzylamines, in the active site, although two binding sites for p-nitrobenzylamine are, identified. We identify structural rearrangements, prior to the H-transfer, step, which are likely to limit the rate of TTQ reduction by benzylamines., This work emphasizes (i) the need for caution when applying, structure-activity correlations to enzyme-catalyzed reactions and (ii) the, added benefit of using both isotope effects and structural analysis, in, conjunction with structure-reactivity relationships, to study chemical, steps in enzyme reaction cycles.
About this StructureAbout this Structure
2HJ4 is a Protein complex structure of sequences from Alcaligenes faecalis with as ligand. Active as Aralkylamine dehydrogenase, with EC number 1.4.99.4 Full crystallographic information is available from OCA.
ReferenceReference
Isotope Effects Reveal That Para-Substituted Benzylamines Are Poor Reactivity Probes of the Quinoprotein Mechanism for Aromatic Amine Dehydrogenase(,)., Hothi P, Roujeinikova A, Khadra KA, Lee M, Cullis P, Leys D, Scrutton NS, Biochemistry. 2007 Jul 18;. PMID:17636875
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