• Title/Summary/Keyword: homoserine acetyltransferase

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Regulation of Enzymes Involved in Methionine Biosynthesis in Corynebacterium glutamicum

  • Yeom, Hye-Jin;Hwang, Byung-Joon;Lee, Myong-Sok;Kim, Youn-Hee;Lee, Heung-Shick
    • Journal of Microbiology and Biotechnology
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    • v.14 no.2
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    • pp.373-378
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    • 2004
  • The regulatory mechanism of methionine biosynthesis in Corynebacterium glutamicum was analyzed at the protein arid gene expression level. O-Acetylhomoserine sulfhydraylase (encoded by metY) was inhibited by 10 mM methionine to a residual activity of 10% level, whereas no such inhibition was found with cystathionine $\gamma$-synthase (encoded by metB) and cystathionine $\beta$-lyase (encoded by metC). The enzymatic activity of homoserine acetyltransferase (encoded by metX) was repressed to a residual activity of 25% level by 10 mM methionine which was added to the growth medium. Cystathionine $\gamma$-synthase and cystathionine $\beta$-lyase were also repressed by 10 mM methionine, but only to a residual activity of 50-70% level. O-Acetylhomoserine sulfhydrylase was very sensitive to repression by 10 mM methionine, showing residual activity of 13%. In addition, homoserine acetyltransferase was also repressed by 10 mM cysteine to 50% of its original activity. No repression of the enzymes by S-adenosyl methionine was observed. The pattern of repression by methionine indicated that the metB and aecD genes might be regulated by a common mechanism, while the metA and metY genes are differently regulated.

Derepression of a Methionine Biosynthetic Gene by Utilizing a Promoter Isolated from Corynebacterium glutamicum (Corynebacterium glutamicum에서 분리된 프로모터를 이용한 메치오닌 생합성 유전자의 조절해제)

  • Park Soo-Dong;Park Ik-Hyun;Choi Jong-Soo;Kim Il-Kwon;Kim Younhee;Lee Heung-Shick
    • Korean Journal of Microbiology
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    • v.41 no.4
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    • pp.300-305
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    • 2005
  • A transcriptionally active fragment $(P_{19})$ isolated by utilizing the promoter-probe shuttle vector pSK1Cat was analyzed. By subcloning analysis, the 180 bp region $(P_{180})$ responsible for the activity was determined. Transcriptional fusion of the C. glutamicum metX gene to $P_{180}\;(P_{180}-metX)$ resulted in a 24-fold increase in MetX activity in a complex medium, while a 13-fold increase was observed with the $P_{tac}$ promoter. Additionally, the expression conferred by $P_{180}$ was not affected by methionine added to the growth medium, suggesting that the $P_{180}$ clone is useful for the deregulated expression of biosynthetic genes in C. glutamicum during amino acid fermentation. Introduction of $P_{180}-metX$ into a lysine-producing C. glutamicum resulted in the production of methionine to 0.8 g/l.