   4.2.1.126 | (R)-lactate + N-acetyl-D-glucosamine 6-phosphate = N-acetylmuramate 6-phosphate + H2O |
the reaction of Haemophilus influenzae MurQ hydrolase proceeds in the reverse direction, reaction mechanism, overview. A ring opening of MurNAc 6P, likely enzyme-catalyzed, first serves to generate the C1 aldehyde and consequently acidifies the hydrogen at the C2 position. This hydrogen is deprotonated by an active site acid/base residue (B1) to generate a resonance-stabilized enolate anion. The enolate then undergoes a syn elimination of D-lactate, aided by a catalytic acid/base residue (B2), to generate a DELTA2,3-unsaturated (E)-alkene intermediate. In a sequence that mirrors the elimination of lactate, B2 first serves to deprotonate an incoming water molecule for addition at the C3 position of the alkene intermediate to generate the enolate anion. This enolate is then protonated at the C2 position by B1 to generate the open chain form of GlcNAc 6P. Ring closure then generates the two anomers of the pyranose form of N-acetyl-D-glucosamine 6-phosphate |
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