Threonine overproduction in yeast strains carrying the HOM3-R2 mutant allele under the control of different inducible promoters.
The HOM3 gene of Saccharomyces cerevisiae codes for aspartate kinase, which plays a crucial role in the regulation of the metabolic flux that leads to threonine biosynthesis. With the aim of obtaining yeast strains able to overproduce threonine in a controlled way, we have placed the HOM3-R2 mutant allele, which causes expression of a feedback-insensitive enzyme, under the control of four distinctive regulatable yeast promoters, namely, PGAL1, PCHA1, PCYC1-HSE2, and PGPH1. The amino acid contents of strains bearing the different constructs were analyzed both under repression and induction conditions. Although some differences in overall threonine production were found, a maximum of around 400 nmol/mg (dry weight) was observed. Other factors, such as excretion to the medium and activity of the catabolic threonine/serine deaminase, also affect threonine accumulation. Thus, improvement of threonine productivity by yeast cells would probably require manipulation of these and other factors.
Farfán
M J
MJ
Departamento de Genética, Facultad de Biología, Universidad de Sevilla, E-41080 Seville, Spain.
Aparicio
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Calderón
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D000483:Alleles; D001222:Aspartate Kinase / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D004271:DNA, Fungal / Q000235:genetics; D015870:Gene Expression; D005800:Genes, Fungal; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010957:Plasmids / Q000235:genetics; D011401:Promoter Regions, Genetic; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism*; D013912:Threonine / Q000096:biosynthesis*; D014170:Transformation, Genetic
D004271:DNA, Fungal; D013912:Threonine; D001222:Aspartate Kinase