Abstract
Vinylglycolate (2-hydroxy-3-butenoic acid, 2) has been found to be an excellent substrate of mandelate racemase. The measured steady-state kinetic parameters for the enantiomers of 2 are comparable, with a maximal racemization rate that is 35% relative to mandelate. Racemization of 2 is subject to a primary deuterium kinetic isotope of about 4, indicating that abstraction of the α-proton is at least partially rate-limiting. Although α-hydroxybutyrate (5), the saturated analogue of 2, is not a substrate, 5 competitively inhibits racemization of 2 with a Ki value comparable to the average Km value for the latter. These results implicate the importance of β,γ-unsaturation in promoting facile racemization of the substrate α-proton. In addition, the enzyme catalyzes the isomerization of 2 to α-ketobutyrate (4), with a partition ratio for racemization/isomerization of about 1 × 104. These observations highlight the precision with which mandelate racemase can promote racemization to the virtual exclusion of a thermodynamically more favored process.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 3347-3351 |
| Number of pages | 5 |
| Journal | Journal of Organic Chemistry |
| Volume | 60 |
| Issue number | 11 |
| DOIs | |
| State | Published - Jun 1 1995 |
Fingerprint
ASJC Scopus subject areas
- Organic Chemistry
Cite this
Racemization of Vinylglycolate Catalyzed by Mandelate Racemase. / Li, Rongshi; Powers, Vincent M.; Kenyon, George L.; Kozarich, John W.
In: Journal of Organic Chemistry, Vol. 60, No. 11, 01.06.1995, p. 3347-3351.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Racemization of Vinylglycolate Catalyzed by Mandelate Racemase
AU - Li, Rongshi
AU - Powers, Vincent M.
AU - Kenyon, George L.
AU - Kozarich, John W.
PY - 1995/6/1
Y1 - 1995/6/1
N2 - Vinylglycolate (2-hydroxy-3-butenoic acid, 2) has been found to be an excellent substrate of mandelate racemase. The measured steady-state kinetic parameters for the enantiomers of 2 are comparable, with a maximal racemization rate that is 35% relative to mandelate. Racemization of 2 is subject to a primary deuterium kinetic isotope of about 4, indicating that abstraction of the α-proton is at least partially rate-limiting. Although α-hydroxybutyrate (5), the saturated analogue of 2, is not a substrate, 5 competitively inhibits racemization of 2 with a Ki value comparable to the average Km value for the latter. These results implicate the importance of β,γ-unsaturation in promoting facile racemization of the substrate α-proton. In addition, the enzyme catalyzes the isomerization of 2 to α-ketobutyrate (4), with a partition ratio for racemization/isomerization of about 1 × 104. These observations highlight the precision with which mandelate racemase can promote racemization to the virtual exclusion of a thermodynamically more favored process.
AB - Vinylglycolate (2-hydroxy-3-butenoic acid, 2) has been found to be an excellent substrate of mandelate racemase. The measured steady-state kinetic parameters for the enantiomers of 2 are comparable, with a maximal racemization rate that is 35% relative to mandelate. Racemization of 2 is subject to a primary deuterium kinetic isotope of about 4, indicating that abstraction of the α-proton is at least partially rate-limiting. Although α-hydroxybutyrate (5), the saturated analogue of 2, is not a substrate, 5 competitively inhibits racemization of 2 with a Ki value comparable to the average Km value for the latter. These results implicate the importance of β,γ-unsaturation in promoting facile racemization of the substrate α-proton. In addition, the enzyme catalyzes the isomerization of 2 to α-ketobutyrate (4), with a partition ratio for racemization/isomerization of about 1 × 104. These observations highlight the precision with which mandelate racemase can promote racemization to the virtual exclusion of a thermodynamically more favored process.
UR - http://www.scopus.com/inward/record.url?scp=0001318631&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0001318631&partnerID=8YFLogxK
U2 - 10.1021/jo00116a017
DO - 10.1021/jo00116a017
M3 - Article
AN - SCOPUS:0001318631
VL - 60
SP - 3347
EP - 3351
JO - Journal of Organic Chemistry
JF - Journal of Organic Chemistry
SN - 0022-3263
IS - 11
ER -