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The protonated form of 1‐ N 6 ‐etheno‐[erythro‐9‐(2‐hydroxy‐3‐nonyl)] adenine is identified at the active site of adenosine deaminase
Author(s) -
Caiolfa Valeria R.,
Gill David,
Parola Abraham H.
Publication year - 1990
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(90)80055-n
Subject(s) - adenosine deaminase , diastereomer , protonation , chemistry , adenosine , stereochemistry , active site , biochemistry , enzyme , organic chemistry , ion
A novel fluorescent competitive inhibitor of adenosine deaminase (EC 3.5.4.4) (ADA), 1‐ N 6 ‐etheno‐[erythro‐9‐(2‐hydroxy‐3‐nonyl)] adenine (ϵ‐EHNA), is protonated at the active site of the enzyme. In ϵ‐EHNA [ K 1 = (4.06 ± 1.00) 10 −6 M] part of the competive 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 ϵ‐EHNA yielded the corrected excitation spectrum of ϵ‐EHNA at the active site of the enzyme. This spectrum mimics that of ϵ‐EHNA at pH 5.5 in buffer solution and is suggested to indicate a shift in protonation equilibrium at the active site.