scholarly journals Kinetic Isotope Effects on Aromatic and Benzylic Hydroxylation byChromobacterium violaceumPhenylalanine Hydroxylase as Probes of Chemical Mechanism and Reactivity†

Biochemistry ◽  
2008 ◽  
Vol 47 (42) ◽  
pp. 11118-11124 ◽  
Author(s):  
Aram J. Panay ◽  
Paul F. Fitzpatrick
Keyword(s):  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Chemical Mechanism ◽  
Kinetic Isotope ◽  
Benzylic Hydroxylation

scholarly journals Transition state for the NSD2-catalyzed methylation of histone H3 lysine 36

2016 ◽  
Vol 113 (5) ◽  
pp. 1197-1201 ◽  
Author(s):  
Myles B. Poulin ◽  
Jessica L. Schneck ◽  
Rosalie E. Matico ◽  
Patrick J. McDevitt ◽  
Michael J. Huddleston ◽  
...  
Keyword(s):  
Transition State ◽  
Isotope Effects ◽  
Histone H3 ◽  
Kinetic Isotope Effects ◽  
Chemical Mechanism ◽  
State Structure ◽  
Transition State Structure ◽  
Chemical Modeling ◽  
Kinetic Isotope ◽  
Human Multiple Myeloma

Nuclear receptor SET domain containing protein 2 (NSD2) catalyzes the methylation of histone H3 lysine 36 (H3K36). It is a determinant in Wolf–Hirschhorn syndrome and is overexpressed in human multiple myeloma. Despite the relevance of NSD2 to cancer, there are no potent, selective inhibitors of this enzyme reported. Here, a combination of kinetic isotope effect measurements and quantum chemical modeling was used to provide subangstrom details of the transition state structure for NSD2 enzymatic activity. Kinetic isotope effects were measured for the methylation of isolated HeLa cell nucleosomes by NSD2. NSD2 preferentially catalyzes the dimethylation of H3K36 along with a reduced preference for H3K36 monomethylation. Primary Me-14C and 36S and secondary Me-3H3, Me-2H3, 5′-14C, and 5′-3H2 kinetic isotope effects were measured for the methylation of H3K36 using specifically labeled S-adenosyl-l-methionine. The intrinsic kinetic isotope effects were used as boundary constraints for quantum mechanical calculations for the NSD2 transition state. The experimental and calculated kinetic isotope effects are consistent with an SN2 chemical mechanism with methyl transfer as the first irreversible chemical step in the reaction mechanism. The transition state is a late, asymmetric nucleophilic displacement with bond separation from the leaving group at (2.53 Å) and bond making to the attacking nucleophile (2.10 Å) advanced at the transition state. The transition state structure can be represented in a molecular electrostatic potential map to guide the design of inhibitors that mimic the transition state geometry and charge.

Chemical Mechanism of a Cysteine Protease, Cathepsin C, As Revealed by Integration of both Steady-State and Pre-Steady-State Solvent Kinetic Isotope Effects

Biochemistry ◽  
2008 ◽  
Vol 47 (33) ◽  
pp. 8697-8710 ◽  
Author(s):  
Jessica L. Schneck ◽  
James P. Villa ◽  
Patrick McDevitt ◽  
Michael S. McQueney ◽  
Sara H. Thrall ◽  
...  
Keyword(s):  
Steady State ◽  
Cysteine Protease ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Chemical Mechanism ◽  
Cathepsin C ◽  
Kinetic Isotope
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