Threonine production by co-existence of cloned genes coding homoserine dehydrogenase and homoserine kinase in Brevibacterium lactofermentum.

Morinaga, Yasushi; Takagi, Hiroshi; Ishida, Masaaki; Miwa, Kiyoshi; Sato, Takaaki; Nakamori, Shigeru; Sano, Konosuke

doi:10.1271/bbb1961.51.93

Cited by 27 publications

(9 citation statements)

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“…The hom gene codes for homoserine dehydrogenase, and alleles of this gene, such as HomG378E [hom(Fbr)], that code for a dehydrogenase which is no longer feedback-inhibited by L-threonine have been identified (34). The overexpression of hom and thrB with high-copy-number plasmids is possible (13,29), whereas hom(Fbr) thrB can only be expressed at low levels (35). This is due to the resulting high internal L-threonine concentration of up to 100 mM, versus less than 1 mM in the wild type.…”

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confidence: 99%

Identification of glyA (Encoding Serine Hydroxymethyltransferase) and Its Use Together with the Exporter ThrE To Increase l -Threonine Accumulation by Corynebacterium glutamicum

Šimić

Willuhn

Sahm

et al. 2002

Appl Environ Microbiol

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L-Threonine can be made by the amino acid-producing bacterium Corynebacterium glutamicum. However, in the course of this process, some of the L-threonine is degraded to glycine. We detected an aldole cleavage activity of L-threonine in crude extracts with an activity of 2.2 nmol min ؊1 (mg of protein) ؊1 . In order to discover the molecular reason for this activity, we cloned glyA, encoding serine hydroxymethyltransferase (SHMT). By using affinity-tagged glyA, SHMT was isolated and its substrate specificity was determined. The aldole cleavage activity of purified SHMT with L-threonine as the substrate was 1.3 mol min ؊1 (mg of protein)؊1 , which was 4% of that with L-serine as substrate. Reduction of SHMT activity in vivo was obtained by placing the essential glyA gene in the chromosome under the control of P tac , making glyA expression isopropylthiogalactopyranoside dependent. In this way, the SHMT activity in an L-threonine producer was reduced to 8% of the initial activity, which led to a 41% reduction in glycine, while L-threonine was simultaneously increased by 49%. The intracellular availability of L-threonine to aldole cleavage was also reduced by overexpressing the L-threonine exporter thrE. In C. glutamicum DR-17, which overexpresses thrE, accumulation of 67 mM instead of 49 mM L-threonine was obtained. This shows that the potential for amino acid formation can be considerably improved by reducing its intracellular degradation and increasing its export.

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confidence: 99%

Identification of glyA (Encoding Serine Hydroxymethyltransferase) and Its Use Together with the Exporter ThrE To Increase l -Threonine Accumulation by Corynebacterium glutamicum

Šimić

Willuhn

Sahm

et al. 2002

Appl Environ Microbiol

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“…Santamaria et al have found that pBL1 of B. lactofermentum is compatible with pCC1 of C. callunae [40]. It was also observed by Morinaga et al that pBL1‐ and pHM1519‐derived plasmids are compatible with each other [41]. In this case, the pBL1‐derived plasmid pAJ 212 was more stably maintained in the host than pAJ 210, a pHM1519 derivative, in the absence of selective pressure, and the latter is gradually lost.…”

Section: Plasmid Incompatibilitymentioning

confidence: 75%

Plasmids of corynebacteria

Deb

Nath

1999

FEMS Microbiology Letters

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Corynebacteria are pleomorphic, asporogenous, Gram-positive bacteria. Included in this group are nonpathogenic soil corynebacteria, which are widely used for the industrial production of amino acids and detergents, and in biotransformation of steroids. Other members of this group are plant and animal pathogens. This review summarizes the current information available about the plasmids of corynebacteria. The emphasis is mainly on the small plasmids, which have been used for construction of vectors for expression of genes in these bacteria. Moreover, considerable information is now available on their nucleotide sequence, gene organization and modes of replication, which would make it possible to further manipulate these plasmids. Other plasmid properties, such as incompatibility and host range, are also discussed. Finally, use of these plasmids as cloning vectors for the expression of heterologous proteins using corynebacteria as hosts is also summarized to highlight the potential of these bacteria as hosts for recombinant DNA.

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“…However, there is an incompatibility problem when two plasmids are constructed with the same vector system and introduced into a bacterial cell. The plasmid co-existence system, as-employed in this paper using two different vectors, can be applied to similar purposes, one of which has been the breeding of a threonine producer of B. lactofermentum by Morinaga et al (1987).…”

Section: Discussionmentioning

confidence: 99%

Molecular breeding of a Brevibacterium lactofermentum l-phenylalanine producer using a cloned prephenate dehydratase gene

Ito

Sato

Matsui

et al. 1990

Appl Microbiol Biotechnol

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The prephenate dehydratase gene was cloned from a mutant of Brevibacterium lactofermenturn, AJl1957 that produced enzyme free from feedback inhibition. The recombinant plasmids pPHI 1 and pPH14 complemented a phenylalanine auxotroph of B. lactofermenturn, A-15, provided the transformant with the desensitized enzyme and caused an increased level of the enzyme compared to that of a wild strain. Plasmid pPH14 was introduced into L-phenylalanine producers genetically induced from Bo lactofermentum; MF358 and FP-1 excreting L-tyrosine and anthranilate, respectively, as by-products. Both transformants predominantly accumulated L-phenylalanine at the expense of by-product formation. Co-existence of pPH14 and pTAR16, a recombinant plasmid expressing desensitized 3-deoxy-D-arabino-hepturosonate-7-phosphate synthase had a marked effect on further improvement in L-phenylalanine productivity, accompanied by an increase in the corresponding enzyme activity. The parent, MF358, accumulating 5.5g/1 L-phenylalanine, 6.8 g/1 L-tyrosine and 0.3 g/1 anthranilate turned into a potent L-phenylalanine producer producing 18.2 g/1 Lphenylalanine and 1.0 g/1 L-tyrosine by-product.

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Threonine production by co-existence of cloned genes coding homoserine dehydrogenase and homoserine kinase in Brevibacterium lactofermentum.

Cited by 27 publications

References 0 publications

Identification of glyA (Encoding Serine Hydroxymethyltransferase) and Its Use Together with the Exporter ThrE To Increase l -Threonine Accumulation by Corynebacterium glutamicum

Identification of glyA (Encoding Serine Hydroxymethyltransferase) and Its Use Together with the Exporter ThrE To Increase l -Threonine Accumulation by Corynebacterium glutamicum

Plasmids of corynebacteria

Molecular breeding of a Brevibacterium lactofermentum l-phenylalanine producer using a cloned prephenate dehydratase gene

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