Molecular and General Genetics MGG

, Volume 164, Issue 3, pp 295-302

Genetic control of invertase formation in Saccharomyces cerevisiae

II. Isolation and characterization of mutants conferring invertase hyperproduction in strain EK-6B carrying the SUC3 gene
  • R. A. HackelAffiliated withBiology Department, Brooklyn College of C.U.N.Y.
  • , N. A. KhanAffiliated withBiology Department, Brooklyn College of C.U.N.Y.

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Invertase formation in the yeast Saccharomyces cerevisiae is subject to repression by hexoses in the growth medium. Mutagen-induced (ethyl methanesulfonate or N-methyl-N'-nitro-nitrosoguanidine) invertase hyperproducer mutants have been derived from the SUC3 MAL3 strain EK-6B by selecting for their ability to grow on media containing the sugar raffinose plus 2-deoxy-D-glucose (2DG). Raffinose like sucrose is a β-fructoside which can be hydrolyzed by yeast invertase (β-fructofuranoside fructohydrolase). These mutants, designated dgr, produce higher levels of invertase (α-glucosidase levels are also elevated but to a lesser extent) under conditions normally repressing invertase biosynthesis in the parent. Invertases of mutants dgr2 and dgr3 are indistinguishable from that of EK-6B with respect to their Km's for sucrose and thermal labilities. Genetic studies revealed that dgr2 and dgr3 are recessive and unlinked to the SUC3 gene.