2OK4

Crystal structure of aromatic amine dehydrogenase TTQ-phenylacetaldehyde adduct oxidized with ferricyanide

Summary for 2OK4

• Entry DOI: 10.2210/pdb2ok4/pdb
• Descriptor: Aromatic amine dehydrogenase, small subunit, Aromatic amine dehydrogenase, large subunit, PHENYLACETALDEHYDE, ... (4 entities in total)
• Functional Keywords: oxidoreductase, ttq
• Biological source: Alcaligenes faecalis; More
• Total number of polymer chains: 4
• Total formula weight: 109304.38

Authors

Roujeinikova, A.,Leys, D. (deposition date: 2007-01-16, release date: 2007-05-01, Last modification date: 2024-11-20)

Primary citation

Roujeinikova, A.,Hothi, P.,Masgrau, L.,Sutcliffe, M.J.,Scrutton, N.S.,Leys, D.
New insights into the reductive half-reaction mechanism of aromatic amine dehydrogenase revealed by reaction with carbinolamine substrates.
J.Biol.Chem., 282:23766-23777, 2007

PubMed Abstract: Aromatic amine dehydrogenase uses a tryptophan tryptophylquinone (TTQ) cofactor to oxidatively deaminate primary aromatic amines. In the reductive half-reaction, a proton is transferred from the substrate C1 to betaAsp-128 O-2, in a reaction that proceeds by H-tunneling. Using solution studies, kinetic crystallography, and computational simulation we show that the mechanism of oxidation of aromatic carbinolamines is similar to amine oxidation, but that carbinolamine oxidation occurs at a substantially reduced rate. This has enabled us to determine for the first time the structure of the intermediate prior to the H-transfer/reduction step. The proton-betaAsp-128 O-2 distance is approximately 3.7A, in contrast to the distance of approximately 2.7A predicted for the intermediate formed with the corresponding primary amine substrate. This difference of approximately 1.0 A is due to an unexpected conformation of the substrate moiety, which is supported by molecular dynamic simulations and reflected in the approximately 10(7)-fold slower TTQ reduction rate with phenylaminoethanol compared with that with primary amines. A water molecule is observed near TTQ C-6 and is likely derived from the collapse of the preceding carbinolamine TTQ-adduct. We suggest this water molecule is involved in consecutive proton transfers following TTQ reduction, and is ultimately repositioned near the TTQ O-7 concomitant with protein rearrangement. For all carbinolamines tested, highly stable amide-TTQ adducts are formed following proton abstraction and TTQ reduction. Slow hydrolysis of the amide occurs after, rather than prior to, TTQ oxidation and leads ultimately to a carboxylic acid product.

PubMed: 17475620
DOI: 10.1074/jbc.M700677200

Experimental method

X-RAY DIFFRACTION (1.45 Å)