Abstract
Δ5-3-Ketosteroid isomerase catalyzes cleavage and formation of a C-H bond at a diffusion-controlled limit. By determining the crystal structures of the enzyme in complex with each of three different inhibitors and by nuclear magnetic resonance (NMR) spectroscopic investigation, we evidenced the ionization of a hydroxyl group (pKa ∼16.5) of an inhibitor, which forms a low barrier hydrogen bond (LBHB) with a catalytic residue Tyr14 (pKa ∼11.5), and the protonation of the catalytic residue Asp38 with pKa of ∼4.5 at pH 6.7 in the interaction with a carboxylate group of an inhibitor. The perturbation of the pKa values in both cases arises from the formation of favorable interactions between inhibitors and catalytic residues. The results indicate that the pKa difference between catalytic residue and substrate can be significantly reduced in the active site environment as a result of the formation of energetically favorable interactions during the course of enzyme reactions. The reduction in the pKa difference should facilitate the abstraction of a proton and thereby eliminate a large fraction of activation energy in general acid/base enzyme reactions. The pKa perturbation provides a mechanistic ground for the fast reactivity of many enzymes and for the understanding of how some enzymes are able to extract a proton from a C-H group with a pKa value as high as ∼30.
| Original language | English |
|---|---|
| Pages (from-to) | 41100-41106 |
| Number of pages | 7 |
| Journal | Journal of Biological Chemistry |
| Volume | 275 |
| Issue number | 52 |
| DOIs | |
| Publication status | Published - 2000 Dec 29 |
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All Science Journal Classification (ASJC) codes
- Biochemistry
- Molecular Biology
- Cell Biology
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Detection of large pKa perturbations of an inhibitor and a catalytic group at an enzyme active site, a mechanistic basis for catalytic power of many enzymes. / Ha, Nam Chul; Kim, Min Sung; Lee, Weontae; Choi, Kwan Yong; Oh, Byung Ha.
In: Journal of Biological Chemistry, Vol. 275, No. 52, 29.12.2000, p. 41100-41106.Research output: Contribution to journal › Article
TY - JOUR
T1 - Detection of large pKa perturbations of an inhibitor and a catalytic group at an enzyme active site, a mechanistic basis for catalytic power of many enzymes
AU - Ha, Nam Chul
AU - Kim, Min Sung
AU - Lee, Weontae
AU - Choi, Kwan Yong
AU - Oh, Byung Ha
PY - 2000/12/29
Y1 - 2000/12/29
N2 - Δ5-3-Ketosteroid isomerase catalyzes cleavage and formation of a C-H bond at a diffusion-controlled limit. By determining the crystal structures of the enzyme in complex with each of three different inhibitors and by nuclear magnetic resonance (NMR) spectroscopic investigation, we evidenced the ionization of a hydroxyl group (pKa ∼16.5) of an inhibitor, which forms a low barrier hydrogen bond (LBHB) with a catalytic residue Tyr14 (pKa ∼11.5), and the protonation of the catalytic residue Asp38 with pKa of ∼4.5 at pH 6.7 in the interaction with a carboxylate group of an inhibitor. The perturbation of the pKa values in both cases arises from the formation of favorable interactions between inhibitors and catalytic residues. The results indicate that the pKa difference between catalytic residue and substrate can be significantly reduced in the active site environment as a result of the formation of energetically favorable interactions during the course of enzyme reactions. The reduction in the pKa difference should facilitate the abstraction of a proton and thereby eliminate a large fraction of activation energy in general acid/base enzyme reactions. The pKa perturbation provides a mechanistic ground for the fast reactivity of many enzymes and for the understanding of how some enzymes are able to extract a proton from a C-H group with a pKa value as high as ∼30.
AB - Δ5-3-Ketosteroid isomerase catalyzes cleavage and formation of a C-H bond at a diffusion-controlled limit. By determining the crystal structures of the enzyme in complex with each of three different inhibitors and by nuclear magnetic resonance (NMR) spectroscopic investigation, we evidenced the ionization of a hydroxyl group (pKa ∼16.5) of an inhibitor, which forms a low barrier hydrogen bond (LBHB) with a catalytic residue Tyr14 (pKa ∼11.5), and the protonation of the catalytic residue Asp38 with pKa of ∼4.5 at pH 6.7 in the interaction with a carboxylate group of an inhibitor. The perturbation of the pKa values in both cases arises from the formation of favorable interactions between inhibitors and catalytic residues. The results indicate that the pKa difference between catalytic residue and substrate can be significantly reduced in the active site environment as a result of the formation of energetically favorable interactions during the course of enzyme reactions. The reduction in the pKa difference should facilitate the abstraction of a proton and thereby eliminate a large fraction of activation energy in general acid/base enzyme reactions. The pKa perturbation provides a mechanistic ground for the fast reactivity of many enzymes and for the understanding of how some enzymes are able to extract a proton from a C-H group with a pKa value as high as ∼30.
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U2 - 10.1074/jbc.M007561200
DO - 10.1074/jbc.M007561200
M3 - Article
C2 - 11007792
AN - SCOPUS:0034731147
VL - 275
SP - 41100
EP - 41106
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
SN - 0021-9258
IS - 52
ER -