TY - JOUR
T1 - Kinetic Isotope Effects and Transition State Structure for Human Phenylethanolamine N-Methyltransferase
AU - Stratton, Christopher F.
AU - Poulin, Myles B.
AU - Du, Quan
AU - Schramm, Vern L.
N1 - Funding Information:
We thank Z. Wang (Einstein) for helpful discussions. This work was supported by research grant GM41916 from the National Institutes of Health.
Publisher Copyright:
© 2016 American Chemical Society.
PY - 2017/2/17
Y1 - 2017/2/17
N2 - Phenylethanolamine N-methyltransferase (PNMT) catalyzes the S-adenosyl-l-methionine (SAM)-dependent conversion of norepinephrine to epinephrine. Epinephrine has been associated with critical processes in humans including the control of respiration and blood pressure. Additionally, PNMT activity has been suggested to play a role in hypertension and Alzheimer's disease. In the current study, labeled SAM substrates were used to measure primary methyl-14C and 36S and secondary methyl-3H, 5′-3H, and 5′-14C intrinsic kinetic isotope effects for human PNMT. The transition state of human PNMT was modeled by matching kinetic isotope effects predicted via quantum chemical calculations to intrinsic values. The model provides information on the geometry and electrostatics of the human PNMT transition state structure and indicates that human PNMT catalyzes the formation of epinephrine through an early SN2 transition state in which methyl transfer is rate-limiting.
AB - Phenylethanolamine N-methyltransferase (PNMT) catalyzes the S-adenosyl-l-methionine (SAM)-dependent conversion of norepinephrine to epinephrine. Epinephrine has been associated with critical processes in humans including the control of respiration and blood pressure. Additionally, PNMT activity has been suggested to play a role in hypertension and Alzheimer's disease. In the current study, labeled SAM substrates were used to measure primary methyl-14C and 36S and secondary methyl-3H, 5′-3H, and 5′-14C intrinsic kinetic isotope effects for human PNMT. The transition state of human PNMT was modeled by matching kinetic isotope effects predicted via quantum chemical calculations to intrinsic values. The model provides information on the geometry and electrostatics of the human PNMT transition state structure and indicates that human PNMT catalyzes the formation of epinephrine through an early SN2 transition state in which methyl transfer is rate-limiting.
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U2 - 10.1021/acschembio.6b00922
DO - 10.1021/acschembio.6b00922
M3 - Article
C2 - 27997103
AN - SCOPUS:85013453437
SN - 1554-8929
VL - 12
SP - 342
EP - 346
JO - ACS Chemical Biology
JF - ACS Chemical Biology
IS - 2
ER -
