Entry M0181 184.108.40.206 phosphonoacetaldehyde hydrolase
Lys53 attacks the carbonyl carbon of the phosphonoacetaldehyde aldehyde in a nucleophilic addition.
Comment: There are two kinetically equivalent routes for the formation of the dipolar intermediate (first step) which give rise to two alternative mechanisms. One in which the native state includes protonated His56 and neutral Lys53 (shown here) and other in which Lys53 is protonated and His56 is neutral. However, the extensive hydrogen bond network that incorporates the proton on the His56 ring (comprising the ring N(1)H of the His56, the backbone carbonyl of Ala45, the N(3)H hydrogen bond to Wat-120, and the hydrogen bond between Wat-120 and the sulfur atom of Met49) may serve to increase the basicity of His56 to a value greater than that of Lys53 when the enzyme is in the closed conformation. Consequently, at neutral pH, which is both the pH optimum for catalysis and the prevailing pH in the cell, His56 is charged and Lys53 is not .
Amino acids involved in the reaction step.
Metal Cofactors involved in Step 01
||Bonds Changed in Order
||Atom Types Involved
The C-O bond changes from a double to single bond
View similar reactions in MACiE.