2.1.1.28	S-adenosyl-L-methionine + phenylethanolamine = S-adenosyl-L-homocysteine + N-methylphenylethanolamine	ordered sequential reaction	639436	
2.1.1.28	S-adenosyl-L-methionine + phenylethanolamine = S-adenosyl-L-homocysteine + N-methylphenylethanolamine	random binding mechanism with a kinetically preferred order of binding where S-adenosyl-L-methionine is the preferred first substrate	639431	
2.1.1.28	S-adenosyl-L-methionine + phenylethanolamine = S-adenosyl-L-homocysteine + N-methylphenylethanolamine	to elucidate the detailed mechanism of enzymatic catalysis of PNMT, combined quantum-mechanical/molecular-mechanical (QM/MM) calculations are performed. The calculation results reveal that this catalysis contains three elementary steps: the deprotonation of protonated norepinphrine, the methyl transferring step and deprotonation of the methylated norepinphrine. The methyl transferring step is proved to be the rate-determining step undergoing a SN2 mechanism with an energy barrier of 16.4 kcal/mol	718999