We argue that Glu-47 is the catalytic base and find, as anticipated, that E47A is catalytically deficient with relatively low kcat,app values.
Catalytic base concentration.
His47 is suitably positioned to act as a catalytic base in the deprotonation of the substrate.
A histidine at position 15 was identified as the catalytic base in the methyl transfer reaction.
Our results indicate that His259 may be the catalytic base for the reaction, and Glu320, Glu287 bracket the catalytic His259.
The optimum activity of AAA at pH > 10 suggests that the reaction mechanism employs Lys84 as the catalytic base to polarize the Ser187 nucleophile in the catalytic triad.
The modeled structure of pAcy1 identified residue D346 as having the strongest impact on the electrostatic features of the catalytic base.
Aspartic acid 24 is the catalytic base that initiates phosphotransfer by deprotonating the acceptor serine, threonine or tyrosine.
The HRD motif (from His143 to Asp145 in hIKK-2) is highly conserved in the kinases, and its arginine residue acts as the catalytic base that drives the phosphorylation event [50], [51].
Several PMF calculations were performed along the reaction pathways selecting either Asp255 or Tyr351 as the catalytic base, and the resulting structures and energetics suggest that Asp255 is the more likely base candidate.
Thus, a glutamic acid at position 363 appeared to function as a catalytic base to enhance cyclosarin reactivation; a glutamine in that position failed to stimulate enzyme activity in the presence of cyclosarin.
