title: The protonated form of 1-N6-etheno-[erythro-9-(2-hydroxy-3-nonyl)] adenine is identified at the active site of adenosine deaminase.
abstract: A novel fluorescent competitive inhibitor of adenosine deaminase (EC 3.5.4.4) (ADA), 1-N6-etheno-[erythro-9-(2-hydroxy-3-nonyl)] adenine (epsilon-EHNA), is protonated at the active site of the enzyme. In epsilon-EHNA [K1 = (4.06 +/- 1.00) 10(-6) M] part of the competitive inhibition of EHNA is combined with spectroscopic properties of etheno-adenines. Computer subtraction of the fluorescence excitation spectrum of ADA from that of its equimolar complex with epsilon-EHNA yielded the corrected excitation spectrum of epsilon-EHNA at the active site of the enzyme. This spectrum mimics that of epsilon-EHNA at pH 5.5 in buffer solution and is suggested to indicate a shift in protonation equilibrium at the active site.
authors: Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
authors: V R
authors: VR
authors: Caiolfa
authors: D
authors: D
authors: Gill
authors: A H
authors: AH
authors: Parola
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives* / Q000032:analysis / Q000494:pharmacology; D000243:Adenosine Deaminase / Q000032:analysis*; D058892:Adenosine Deaminase Inhibitors; D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D003201:Computers; D005454:Fluorescence Polarization; D006863:Hydrogen-Ion Concentration; D009700:Nucleoside Deaminases / Q000032:analysis*; D011522:Protons; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet
chemical_list: D058892:Adenosine Deaminase Inhibitors; D011522:Protons; C010192:9-(2-hydroxy-3-nonyl)adenine; D009700:Nucleoside Deaminases; D000243:Adenosine Deaminase; D000225:Adenine