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The glmS ribozyme is a unique known natural catalytic RNA that takes advantage of a small molecule coenzyme,glucosamine 6-phosphate(GlcN6P).However,the role of GlcN6P in the catalytic mechanism has not been determined conclusively.In the present work,the possible mechanisms were investigated at the M062X/6-31+G(d,p)level and including the solvation of water through the SMD continuum models.Single-point computations at the SMD-M06-2X/6-311+G(2df,2p)level was performed for more precise energy predictions.Two possible pathways,the first pathway(path A)is that the protonated form of GlcN6P serves as the general acid.The other pathway(path B)is that the unprotonated form of GlcN6P serves as the general base to catalyze the reaction through two tightly bound water.Our results indicate that path A is more favorable than path B in solvent.That is,GlcN6P acts as a general acid catalyst.Moreover,in path A,nucleophilic attack of the O2 with the proton-transfer of O2─H is the rate-determining step.