(24S)-25-epoxycholesterol + oxidized [NADPH--hemoprotein reductase] + H2O + H(+) => desmosterol + reduced [NADPH--hemoprotein reductase] + O2
(24s)-25-epoxycholesterol + oxidized [nadph--hemoprotein reductase] + h2o + h(+) => desmosterol + reduced [nadph--hemoprotein reductase] + o2