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Results 1 - 10 of 10
EC Number
Reaction
Commentary
Reference
L-proline = D-proline
a new combined quantum mechanical and molecular mechanical (QM/MM) potential to study the reaction mechanism of proline racemase is used. Three critical points are identified: two almost isoenergetic minima (M1a and M2a), in which the enzyme is bound to L- and D-Pro, respectively, and a transition state (TSCa), unveiling a highly asynchronous concerted process; quantum mechanical and molecular mechanical study reveals two almost isoenergetic minima M1a and M2a, in which the enzyme is bound to L-proline and D-proline, respectively, and a transition state TSCa, unveiling a highly asynchronous concerted process. Residues Asn133, Asp296, and Gly301 destabilize M2a. Conversely, both Gly131and Gly303 stabilize M2a. Residues Gly131, Gly301, and Thr302 stabilize TSCa
L-proline = D-proline
energetics of proline racemase: transition-state fractionation factors for the two protons involved in the catalytic steps
L-proline = D-proline
enzyme exists in two states, one of which binds and isomerizes L-Pro and the other of which binds and isomerizes D-Pro. It seems likely that the two enzyme forms differ only in the protonation states of the acidic and basic groups at the active site
L-proline = D-proline
fractionation factors for the essential catalytic groups in the enzyme-substrate complexes
L-proline = D-proline
mechanism
L-proline = D-proline
mechanism is best accomodated by a route that involves a transition state or unstable intermediate in which the proline carbanion is flanked by the two catalytic thiols of the enzyme
L-proline = D-proline
racemization is accompanied by deuterium incorporation from the solvent into the alpha position of Pro, participation of two equivalent hydrogen acceptor sites
L-proline = D-proline
stepwise reaction for the interconversion of the free enzyme forms in which a proton is abstracted from a bound water molecule to give a reaction intermediate having a hydroxide ion bound to the diprotonated form of the enzyme
L-proline = D-proline
the substrate and product 'on-off' steps are faster than the racemization step and the racemization reaction proceeds either in a concerted manner or in a stepwise fashion involving enzyme catalytic groups, e.g. thiols
L-proline = D-proline
two-base mechanism in which one base on the enzyme removes the substrate alpha-hydrogen as a proton and the conjugate acid of another base donates a proton to the opposite side of the alpha-carbon
Results 1 - 10 of 10