Subcellular Distribution of Yeast Invertase Isoenzymes

Homogenates from yeast cells contain 1% or less of sedimentable invertase activity. Sedimentability is equally low in homogenates from cells repressed or derepressed with regard to invertase secretion. Intracellulary, the mannanprotein form of invertase is largely localized in vacuoles whereas the small isoenzyme is largely present in the soluble cell fraction. These findings indicate that vesicles are not involved in the secretion of invertase. A soluble mode of invertase secretion is discussed.