Non-Utilization of sucrose by the petite mutant of a distiller's yeast

Summary A number of yeast strains are known to be unable to metabolize several sugars (galactose, maltose, -methylglucoside) when converted to their petite mutants. The basis of this phenomenon is considered to be the loss of the ability to transport the sugars across the cell membrane. However, sucrose is believed to be hydrolyzed before the products are transported into the cell, and the enzyme responsible (invertase) is thought to be either present in the periplasmic space or to be bound to the outer surface of the cytoplasmic membrane. Hence the loss of the ability to metabolize sucrose may infer the impairment of the mechanism for transport of invertase to its normal location outside the cytoplasm. We have found a distiller's yeast strain which has lost the ability to metabolize sucrose when it is converted to the petite mutant, and we report here some of its properties. We have shown that the cell produces invertase, which is present in the cell-free extract, but not in the pellet of cell walls and unbroken cells, though we have not determined whether the enzyme is present in the cytoplasm in the glycosylated or the unglycosylated form. The ability of the strain to ferment sucrose is also impaired in respiratory-competent cells, when the determination is made under anaerobic conditions.