Elusive transition state of alcohol dehydrogenase unveiled.
For several decades the hydride transfer catalyzed by alcohol dehydrogenase has been difficult to understand. Here we add to the large corpus of anomalous and paradoxical data collected for this reaction by measuring a normal (> 1) 2 degrees kinetic isotope effect (KIE) for the reduction of benzaldehyde. Because the relevant equilibrium effect is inverse (< 1), this KIE eludes the traditional interpretation of 2 degrees KIEs. It does, however, enable the development of a comprehensive model for the "tunneling ready state" (TRS) of the reaction that fits into the general scheme of Marcus-like models of hydrogen tunneling. The TRS is the ensemble of states along the intricate reorganization coordinate, where H tunneling between the donor and acceptor occurs (the crossing point in Marcus theory). It is comparable to the effective transition state implied by ensemble-averaged variational transition state theory. Properties of the TRS are approximated as an average of the individual properties of the donor and acceptor states. The model is consistent with experimental findings that previously appeared contradictory; specifically, it resolves the long-standing ambiguity regarding the location of the TRS (aldehyde-like vs. alcohol-like). The new picture of the TRS for this reaction identifies the principal components of the collective reaction coordinate and the average structure of the saddle point along that coordinate.
Roston
Daniel
D
Department of Chemistry, University of Iowa, Iowa City, IA 52242, USA.
Kohen
Amnon
A
D000426:Alcohol Dehydrogenase / Q000737:chemistry* / Q000378:metabolism; D000438:Alcohols / Q000737:chemistry / Q000378:metabolism; D000447:Aldehydes / Q000737:chemistry / Q000378:metabolism; D001547:Benzaldehydes / Q000737:chemistry / Q000378:metabolism; D055162:Biocatalysis; D006859:Hydrogen / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D008968:Molecular Conformation; D010084:Oxidation-Reduction; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D013379:Substrate Specificity
D000438:Alcohols; D000447:Aldehydes; D001547:Benzaldehydes; D006859:Hydrogen; D000426:Alcohol Dehydrogenase; C032175:benzaldehyde
Eur J Biochem. 2002 Jul;269(13):3113-21
12084051
Biochemistry. 1996 Oct 1;35(39):12873-81
8841131
Science. 2006 Apr 14;312(5771):237-41
16614214
Chem Phys. 2005 Dec 7;319(1-3):283-296
21132078
J Am Chem Soc. 2005 Oct 26;127(42):14879-86
16231943
Nature. 1999 Jun 3;399(6735):496-9
10365965
Chem Rev. 2006 Aug;106(8):3095-118
16895320
J Am Chem Soc. 2002 Apr 17;124(15):3858-64
11942822
Chem Rev. 2006 Aug;106(8):3140-69
16895322
J Am Chem Soc. 2008 Jun 4;130(22):7092-7
18470990
Biochemistry. 1980 May 13;19(10):2005-16
6990968
Acc Chem Res. 2006 Feb;39(2):93-100
16489728
Biochemistry. 1993 Jun 1;32(21):5503-7
8504071
J Am Chem Soc. 2008 May 21;130(20):6577-85
18426205
Biochemistry. 1993 Oct 19;32(41):11186-94
8218182
J Biol Chem. 1972 Dec 25;247(24):7977-87
4344986
Chem Biol Interact. 2009 Mar 16;178(1-3):16-23
19022233
Chem Rev. 2006 Aug;106(8):3210-35
16895325
Biochemistry. 1976 May 4;15(9):2018-26
773429
Biochemistry. 1981 Mar 31;20(7):1817-25
7013802
J Phys Chem B. 2007 Jun 21;111(24):6643-54
17497918
Science. 1989 Mar 10;243(4896):1325-30
2646716
Philos Trans R Soc Lond B Biol Sci. 2006 Aug 29;361(1472):1323-31
16873120
Biochemistry. 1999 Apr 6;38(14):4398-402
10194359
Biochem J. 1978 Jun 1;171(3):629-37
208510
J Am Chem Soc. 2006 Nov 1;128(43):14053-8
17061887