The overall mechanism of<unk> . The<unk>  mechanism proceeds through an E2 elimination. This elimination is initiated by a glutamate residue, which, while necessary for the mechanism, is not conserved. The residue appears in a wide range of locations within the different types of the enzyme (it is Glu 376 in MCAD). The glutamate residue deprotonates the pro-R hydrogen of the alpha carbon. Hydrogen bonding of the substrate’s carbonyl oxygen to both the 2’-OH of the ribityl side-chain of FAD and to the main chain N-H of the previously mentioned glutamate residue lowers the pKa of this proton, allowing it to be readily removed by glutamate. Close-up of the medium-chain<unk>  active site. FAD is bound. The substrate will bind in the space between Glu-376 and FAD when fatty acid oxidation is initialized. PDB code: 3mdd. As the alpha carbon is being deprotonated, the pro-R hydrogen of the beta carbon leaves as a hydride to FAD in a concerted step. It adds to the Re face of FAD at the N-5 position, and the enzyme holds FAD in place through hydrogen bonding with the pyrimidine portion and hydrophobic interactions with the dimethylbenzene portion. The substrate has now been transformed into an α,β unsaturated thioester. As FAD picks up the hydride, the carbonyl oxygen adjacent to the N-1 nitrogen becomes negatively charged. These electrons are in resonance with the N-1 nitrogen, distributing and stabilizing the resulting negative charge. The charge is also stabilized by hydrogen bonding between the oxygen and nitrogen of interest and various residues within the enzyme.
Acyl-CoA dehydrogenase
Pyruvate carboxylase
Phenylalanine hydroxylase
Aldehyde dehydrogenase
Glutamate dehydrogenase
Butyrate esterase
Glycogen phosphorylase isoenzyme BB
Monoamine oxidase B