title: Kinetic Isotope Effects and Transition State Structure for Human Phenylethanolamine N-Methyltransferase.
abstract: 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 and36S 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.
authors.affiliation: Department of Biochemistry, Albert Einstein College of Medicine , 1300 Morris Park Avenue, Bronx, New York 10461, United States.
authors.forename: Christopher F
authors.initials: CF
authors.lastname: Stratton
authors.affiliation: Department of Biochemistry, Albert Einstein College of Medicine , 1300 Morris Park Avenue, Bronx, New York 10461, United States.
authors.forename: Myles B
authors.identifier: 0000-0002-3789-703X
authors.initials: MB
authors.lastname: Poulin
authors.affiliation: Department of Biochemistry, Albert Einstein College of Medicine , 1300 Morris Park Avenue, Bronx, New York 10461, United States.
authors.forename: Quan
authors.initials: Q
authors.lastname: Du
authors.affiliation: Department of Biochemistry, Albert Einstein College of Medicine , 1300 Morris Park Avenue, Bronx, New York 10461, United States.
authors.forename: Vern L
authors.identifier: 0000-0002-8056-1929
authors.initials: VL
authors.lastname: Schramm
mesh_terms: D006801:Humans; D007554:Isotopes; D007700:Kinetics; D010625:Phenylethanolamine N-Methyltransferase / Q000737:chemistry*; D011487:Protein Conformation
chemical_list: D007554:Isotopes; D010625:Phenylethanolamine N-Methyltransferase