CHARACTERIZATION OF HYDROGEN-BONDING IN THE COMPLEX OF ADENOSINE-DEAMINASE WITH A TRANSITION-STATE ANALOG - A RAMAN-SPECTROSCOPIC STUDY

Citation
H. Deng et al., CHARACTERIZATION OF HYDROGEN-BONDING IN THE COMPLEX OF ADENOSINE-DEAMINASE WITH A TRANSITION-STATE ANALOG - A RAMAN-SPECTROSCOPIC STUDY, Biochemistry, 37(14), 1998, pp. 4968-4976
Citations number
32
Categorie Soggetti
Biology
Journal title
ISSN journal
00062960
Volume
37
Issue
14
Year of publication
1998
Pages
4968 - 4976
Database
ISI
SICI code
0006-2960(1998)37:14<4968:COHITC>2.0.ZU;2-P
Abstract
The Raman spectra of purine ribonucleoside as well as a stable model c ompound (1-methoxyl-1,6-dihydropurine ribonucleoside), free in solutio n and bound into its complex with adenosine deaminase (ADA), have been studied by Raman difference spectroscopy. Using purine riboside analo gues labeled with (15)N1 or (13)C6 and the theoretical frequency norma l-mode analyses of these molecules using ab initio quantum mechanic me thods, we have positively identified many of the Raman bands in the en zyme-bound inhibitor. The spectrum of the enzyme-bound inhibitor is co nsistent with the enzyme-catalyzed hydration of the purine base to yie ld 1-hydroxyl-1,6-dihydropurine ribonucleoside, as suggested earlier b y X-ray crystallographic studies. In addition, the Raman data and subs equent vibrational analyses show that the binding-induced Raman spectr al changes of the inhibitor can be modeled by the formation of a stron g hydrogen bond to its N1-H bond. This hydrogen bond, apparently betwe en the N1-H of the inhibitor and the O delta 1 of Glu217 in ADA, cause s a substantial N1-H bending frequency increase of about 50-100 cm(-1) compared to its solution value, and this results in an estimated enth alpy of the hydrogen bond of 4-10 kcal/mol. The relationship of transi tion state stabilization in the catalytic strategy of this efficient e nzyme to such a bonding pattern is discussed.