Affiliation:
1. Institut für Biotechnologie 1 des Forschungszentrums Jülich GmbH, D-5170 Jülich, Federal Republic of Germany
Abstract
The gene cluster that codes for feedback-resistant aspartate kinase (
lysC
α and
lysC
β) and aspartate semialdehyde dehydrogenase (
asd
) was cloned from a mutant strain of
Corynebacterium glutamicum.
Its functional analysis by subcloning, enzyme assays, and type of aspartate kinase regulation enabled the isolation of a fragment for separate expression of the feedback-resistant kinase without aspartate semialdehyde dehydrogenase expression. This was used together with other clones constructed (J. Cremer, L. Eggeling, and H. Sahm, Mol. Gen. Genet. 220:478-480, 1990) to overexpress individually each of the six genes that convert aspartate to lysine. Analysis of lysine formation revealed that overexpression of the feedback-resistant kinase alone suffices to achieve lysine formation (38 mM). Also, sole overexpression of wild-type dihydrodipicolinate synthase resulted in lysine formation but in a lower amount (11 mM). The other four enzymes had no effect on lysine secretion. With a plasmid overexpressing both relevant enzymes together, a further increase in lysine yield was obtained. This shows that of the six enzymes that convert aspartate to lysine the kinase and the synthase are responsible for flow control in the wild-type background and can be useful for construction of lysine-producing strains.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
149 articles.
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