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Applied and Environmental Microbiology, January 1999, p. 110-116, Vol. 65, No. 1
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.

Threonine Overproduction in Yeast Strains Carrying the HOM3-R2 Mutant Allele under the Control of Different Inducible Promoters

María-José Farfán, Luis Aparicio, and Isabel L. Calderón*

Departamento de Genética, Facultad de Biología, Universidad de Sevilla, E-41080 Seville, Spain

Received 22 July 1998/Accepted 16 October 1998

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.

* Corresponding author. Mailing address: Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Ap. 1095, E-41080 Sevilla, Spain. Phone: 34-954557108. Fax: 34-954557104. E-mail: genilc{at}cica.es.

Applied and Environmental Microbiology, January 1999, p. 110-116, Vol. 65, No. 1
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.


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