TY - JOUR
T1 - Purification, characterization and inhibition of sterol C24-methyltransferase from Candida albicans
AU - Ganapathy, Kulothungan
AU - Kanagasabai, Ragu
AU - Nguyen, Thi Thuy Minh
AU - Nes, W. David
N1 - Funding Information:
This research was supported in part by grants from the National Science Foundation (MCB-0417436 and 0929212). The technical assistance of Dr. Wenxu Zhou during the early phases of this work is greatly appreciated.
PY - 2011/1/15
Y1 - 2011/1/15
N2 - Solubilized sterol C24-methyltransferase (24-SMT) was purified to homogeneity from a cell extract of the yeast Candida albicans (Ca) by anion exchange chromatography, gel permeation chromatography and fast performance liquid chromatography using a Mono Q column. The purified enzyme has an apparent molecular mass of 178 kDa on gel permeation chromatography and 43 kDa on SDS/PAGE, indicating that it is composed of four identical subunits. The substrate requirement of the native enzyme has an optimal specificity for zymosterol with associated kinetic constants of Km 50 μM and kcat of 0.01 s-1. The product of the enzyme incubated with zymosterol was fecosterol. Inhibition of the catalyst was observed with substrate analogs designed as transition state analogs (25-azalanosterol, K i = 54 nM and 24 (R,S),25-epiminolanosterol, Ki = 11 nM) or as mechanism-based inactivators (26,27-dehydrozymosterol, Ki 9 μM) and kinact = 0.03 min-1) of the C24-methylation reaction. Product analogs ergosterol and fecosterol, but neither cholesterol nor sitosterol, inhibited activity affording Ki values of 20 and 72 μM, respectively. Ammonium and thia analogs of the intermediates of the sterol C24-methyl reaction sequence were effective growth inhibitors exhibiting IC50 values that ranged from 3 to 20 μM.
AB - Solubilized sterol C24-methyltransferase (24-SMT) was purified to homogeneity from a cell extract of the yeast Candida albicans (Ca) by anion exchange chromatography, gel permeation chromatography and fast performance liquid chromatography using a Mono Q column. The purified enzyme has an apparent molecular mass of 178 kDa on gel permeation chromatography and 43 kDa on SDS/PAGE, indicating that it is composed of four identical subunits. The substrate requirement of the native enzyme has an optimal specificity for zymosterol with associated kinetic constants of Km 50 μM and kcat of 0.01 s-1. The product of the enzyme incubated with zymosterol was fecosterol. Inhibition of the catalyst was observed with substrate analogs designed as transition state analogs (25-azalanosterol, K i = 54 nM and 24 (R,S),25-epiminolanosterol, Ki = 11 nM) or as mechanism-based inactivators (26,27-dehydrozymosterol, Ki 9 μM) and kinact = 0.03 min-1) of the C24-methylation reaction. Product analogs ergosterol and fecosterol, but neither cholesterol nor sitosterol, inhibited activity affording Ki values of 20 and 72 μM, respectively. Ammonium and thia analogs of the intermediates of the sterol C24-methyl reaction sequence were effective growth inhibitors exhibiting IC50 values that ranged from 3 to 20 μM.
KW - Antifungal agents
KW - Ergosterol biosynthesis
KW - Membranes
KW - Sterol C24-methyltransferase
KW - Sterol inhibitors
KW - Suicide substrates
UR - http://www.scopus.com/inward/record.url?scp=78651227502&partnerID=8YFLogxK
U2 - 10.1016/j.abb.2010.10.008
DO - 10.1016/j.abb.2010.10.008
M3 - Article
C2 - 20946868
AN - SCOPUS:78651227502
SN - 0003-9861
VL - 505
SP - 194
EP - 201
JO - Archives of Biochemistry and Biophysics
JF - Archives of Biochemistry and Biophysics
IS - 2
ER -