Subcellular Localization of the Enzymes Involved in the Late Stage of Ergosterol Biosynthesis in Yeast1

Abstract

The subcellular distribution of enzymes involved in the reaction sequence from zymosterol to ergosterol was studied. The spheroplasts obtained from cells aero-bically grown on ethanol were gently disrupted and the homogenate was fractionated into the subcellular organelles by differential centrifugation. Inspection of the distribution of several marker enzymes revealed that the fractionation was reasonably effected. As a result of experiments, Δ⁸-Δ⁷-sterol isomerase, S-adenosylmethio-nine: Δ²⁴-steroI methyltransferase and the enzyme involved in the reaction sequence from episterol to ergosterol were localized in microsomes. These results suggest the localization of enzymes involved in the late stage of ergosterol synthesis in microsomes.