[Transport and utilization of alditols in the yeast Rhodotorula gracilis glutinis (author's transl)]

Abstract

Although alditols reached the interior of the cells of Rhodotorula gracilis by means of the constitutive monosaccharide carrier, a second carrier of pentitols was found to be inducible. Ribitol and L-arabinitol, entering the cells by the constitutive carrier, induced a single catabolic enzyme system, including a carrier of pentitols. This induction depended on de novo protein synthesis. In addition to ribitol and L-arabinitol, the induced catabolic enzyme system was also specific for xylitol and D-arabinitol; these two alditols were not inducers. Hexitols, erythritol and pentoses were not transported or catabolized by the induced system. The induced carrier had a lower half-saturation constant, KT, and higher maximal velocity, V, than the constitutive carrier of penitols. Kinetic studies of induced transport indicated, that this was an active process which appeared to be coupled with the simultaneous uptake of H+-ions (H+-substrate symport). The induced transport of pentitols was strongly inhibited by monosaccharides, although not competitively. The enzyme synthesis induced by ribitol or L-arabinitol was repressed by monosaccharides.