TY - JOUR
T1 - Mechanism-based active site modification of the soybean sterol methyltransferase by 26,27-dehydrocycloartenol
AU - Song, Zhihong
AU - Zhou, Wenxu
AU - Liu, Jialin
AU - Nes, W. David
N1 - Funding Information:
This work was supported by the National Science Foundation (MCB 011540 and IBN 0115401) and the Welch Foundation (D-1276). The assistance of Mathew Miller is appreciated.
PY - 2004/1/5
Y1 - 2004/1/5
N2 - 26,27-Dehydrocycloartenol (26,27-DHC) was shown to be a substrate for the soybean sterol methyltransferase (SMT) as well as a mechanism-based inhibitor of enzyme action. The Km and kcat for 26,27-DHC was 10 μM and 0.018 min-1, respectively. SMT catalyzed 26,27-DHC to two products tentatively identified as 26-homocholesta-9,19-cyclo-23(24)E, 26(26′)-dienol and 26-homocholesta-9,19-cyclo-26(26′)-en-3β, 24β-diol by GC-MS. Inhibitor treatment was concentration- and time-dependent (pseudo-first-order kinetics). A replot of the half-lives for inactivation versus the inverse of the inactivator concentrations gave an apparent Ki of 42 μM and a maximum rate of inactivation of 0.29 min-1. A partition ratio (kcat/kinact) was calculated to be 0.06.
AB - 26,27-Dehydrocycloartenol (26,27-DHC) was shown to be a substrate for the soybean sterol methyltransferase (SMT) as well as a mechanism-based inhibitor of enzyme action. The Km and kcat for 26,27-DHC was 10 μM and 0.018 min-1, respectively. SMT catalyzed 26,27-DHC to two products tentatively identified as 26-homocholesta-9,19-cyclo-23(24)E, 26(26′)-dienol and 26-homocholesta-9,19-cyclo-26(26′)-en-3β, 24β-diol by GC-MS. Inhibitor treatment was concentration- and time-dependent (pseudo-first-order kinetics). A replot of the half-lives for inactivation versus the inverse of the inactivator concentrations gave an apparent Ki of 42 μM and a maximum rate of inactivation of 0.29 min-1. A partition ratio (kcat/kinact) was calculated to be 0.06.
UR - http://www.scopus.com/inward/record.url?scp=0348147645&partnerID=8YFLogxK
U2 - 10.1016/j.bmcl.2003.10.015
DO - 10.1016/j.bmcl.2003.10.015
M3 - Article
C2 - 14684292
AN - SCOPUS:0348147645
VL - 14
SP - 33
EP - 36
JO - Bioorganic and Medicinal Chemistry Letters
JF - Bioorganic and Medicinal Chemistry Letters
SN - 0960-894X
IS - 1
ER -