The assignment of downfield proton resonances in an enzyme inhibitor complex using time-dependent saturation transferred NOEs.
Journal - Journal of the American Chemical Society (United States )
We have used time-dependent saturation transferred NOE (STNOE) measurements to assign two downfield resonances in the proton spectrum of an adenosine deaminase-purine riboside mixture. Our results show that this method can be used to detect structural changes that occur upon inhibitor binding to the enzyme and to determine which protons of the bound inhibitor are strongly hydrogen bonded in the complex.
|ISSN : ||0002-7863|
|Mesh Heading : ||Adenosine Deaminase Binding, Competitive Enzyme Inhibitors Nuclear Magnetic Resonance, Biomolecular Protons Purine Nucleosides Ribonucleosides metabolism chemistry metabolism metabolism metabolism|
|Mesh Heading Relevant : ||antagonists & inhibitors chemistry methods chemistry chemistry|
A vibrational structure of 7,8-dihydrobiopterin bound to dihydroneopterin aldolase.
Journal - The Journal of biological chemistry (UNITED STATES )
Dihydroneopterin aldolase (DHNA) catalyzes the conversion of 7, 8-dihydroneopterin to 6-hydroxymethyl-7,8-dihydropterin and glycolaldehyde. An inhibitor of the enzyme, 7,8-dihydrobiopterin, free in solution and bound in its complex with the enzyme has been studied by Raman difference spectroscopy. By using isotopically labeled 7,8-dihydrobiopterin and normal mode analyses based on ab initio quantum mechanic methods, we have positively identified some of the Raman bands in the enzyme-bound inhibitor, particularly the important N5=C6 stretch mode. The spectrum of the enzyme-bound inhibitor shows that the pK(a) of N5 is not significantly increased in the complex. This result suggests that N5 of 7,8-dihydroneopterin is not protonated before the bond cleavage of 7,8-dihydroneopterin during the DHNA-catalyzed reaction as has been suggested. Our results also show that the N5=C6 stretch mode of 7, 8-dihydrobiopterin shifts 19 cm(-)(1) upon binding to DHNA. Various possibilities on how the enzyme can bring about such large frequency change of the N5=C6 stretch mode are discussed.
|ISSN : ||0021-9258|
|Mesh Heading : ||Aldehyde-Lyases Binding Sites Biopterin Spectrophotometry, Ultraviolet Spectrum Analysis, Raman chemistry|
|Mesh Heading Relevant : ||antagonists & inhibitors analogs & derivatives|