2Q7Q

Crystal structure of Alcaligenes faecalis AADH in complex with p-chlorobenzylamine.

Summary for 2Q7Q

• Entry DOI: 10.2210/pdb2q7q/pdb
• Descriptor: Aralkylamine dehydrogenase light chain, Aralkylamine dehydrogenase heavy chain, 1-(4-CHLOROPHENYL)METHANAMINE, ... (4 entities in total)
• Functional Keywords: oxidoreductase, ttq
• Biological source: Alcaligenes faecalis; More
• Cellular location: Periplasm : P84887 P84888
• Total number of polymer chains: 4
• Total formula weight: 107737.83

Authors

Roujeinikova, A.,Leys, D. (deposition date: 2007-06-07, release date: 2007-07-31, Last modification date: 2017-10-18)

Primary citation

Hothi, P.,Roujeinikova, A.,Khadra, K.A.,Lee, M.,Cullis, P.,Leys, D.,Scrutton, N.S.
Isotope effects reveal that para-substituted benzylamines are poor reactivity probes of the quinoprotein mechanism for aromatic amine dehydrogenase.
Biochemistry, 46:9250-9259, 2007

PubMed Abstract: 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.

PubMed: 17636875
DOI: 10.1021/bi7007239

Experimental method

X-RAY DIFFRACTION (1.6 Å)