scholarly journals Valine biosynthesis in Saccharomyces cerevisiae is regulated by the mitochondrial branched-chain amino acid aminotransferase Bat1

2018 ◽  
Vol 5 (6) ◽  
pp. 293-299 ◽  
Author(s):  
Natthaporn Takpho ◽  
Daisuke Watanabe ◽  
Hiroshi Takagi
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Amino Acid ◽  
Branched Chain Amino Acid ◽  
Valine Biosynthesis ◽  
Branched Chain

scholarly journals The Saccharomyces cerevisiae Leu3 protein activates expression of GDH1, a key gene in nitrogen assimilation.

1995 ◽  
Vol 15 (1) ◽  
pp. 52-57 ◽  
Author(s):  
Y Hu ◽  
T G Cooper ◽  
G B Kohlhaw
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Amino Acid ◽  
Glutamate Dehydrogenase ◽  
Specific Activity ◽  
Yeast Cells ◽  
Homologous Sequence ◽  
Biosynthetic Pathways ◽  
Lacz Expression ◽  
Branched Chain Amino Acid ◽  
Branched Chain

The Leu3 protein of Saccharomyces cerevisiae has been shown to be a transcriptional regulator of genes encoding enzymes of the branched-chain amino acid biosynthetic pathways. Leu3 binds to upstream activating sequences (UASLEU) found in the promoters of LEU1, LEU2, LEU4, ILV2, and ILV5. In vivo and in vitro studies have shown that activation by Leu3 requires the presence of alpha-isopropylmalate. In at least one case (LEU2), Leu3 actually represses basal-level transcription when alpha-isopropylmalate is absent. Following identification of a UASLEU-homologous sequence in the promoter of GDH1, the gene encoding NADP(+)-dependent glutamate dehydrogenase, we demonstrate that Leu3 specifically interacts with this UASLEU element. We then show that Leu3 is required for full activation of the GDH1 gene. First, the expression of a GDH1-lacZ fusion gene is three- to sixfold lower in a strain lacking the LEU3 gene than in an isogenic LEU3+ strain. Expression is restored to near-normal levels when the leu3 deletion cells are transformed with a LEU3-bearing plasmid. Second, a significant decrease in GDH1-lacZ expression is also seen when the UASLEU of the GDH1-lacZ construct is made nonfunctional by mutation. Third, the steady-state level of GDH1 mRNA decreases about threefold in leu3 null cells. The decrease in GDH1 expression in leu3 null cells is reflected in a diminished specific activity of NADP(+)-dependent glutamate dehydrogenase. We also demonstrate that the level of GDH1-lacZ expression correlates with the cells' ability to generate alpha-isopropylmalate and is lowest in cells unable to produce alpha-isopropylmalate. We conclude that GDH1, which plays an important role in the assimilation of ammonia in yeast cells, is, in part, activated by a Leu3-alpha-isopropylmalate complex. This conclusion suggests that Leu3 participates in transcriptional regulation beyond the branched-chain amino acid biosynthetic pathways.

scholarly journals Linking Central Metabolism with Increased Pathway Flux: l-Valine Accumulation by Corynebacterium glutamicum

2002 ◽  
Vol 68 (5) ◽  
pp. 2246-2250 ◽  
Author(s):  
Eva Radmacher ◽  
Adela Vaitsikova ◽  
Udo Burger ◽  
Karin Krumbach ◽  
Hermann Sahm ◽  
...  
Keyword(s):  
Amino Acid ◽  
Corynebacterium Glutamicum ◽  
Acid Synthesis ◽  
Acetohydroxy Acid Synthase ◽  
Amino Acid Synthesis ◽  
Branched Chain Amino Acid ◽  
In The Wild ◽  
Valine Biosynthesis ◽  
Branched Chain ◽  
Pathway Flux

ABSTRACT Mutants of Corynebacterium glutamicum were made and enzymatically characterized to clone ilvD and ilvE, which encode dihydroxy acid dehydratase and transaminase B, respectively. These genes of the branched-chain amino acid synthesis were overexpressed together with ilvBN (which encodes acetohydroxy acid synthase) and ilvC (which encodes isomeroreductase) in the wild type, which does not excrete l-valine, to result in an accumulation of this amino acid to a concentration of 42 mM. Since l-valine originates from two pyruvate molecules, this illustrates the comparatively easy accessibility of the central metabolite pyruvate. The same genes, ilvBNCD, overexpressed in an ilvA deletion mutant which is unable to synthesize l-isoleucine increased the concentration of this amino acid to 58 mM. A further dramatic increase was obtained when panBC was deleted, making the resulting mutant auxotrophic for d-pantothenate. When the resulting strain, C. glutamicum 13032ΔilvAΔpanBC with ilvBNCD overexpressed, was grown under limiting conditions it accumulated 91 mM l-valine. This is attributed to a reduced coenzyme A availability and therefore reduced flux of pyruvate via pyruvate dehydrogenase enabling its increased drain-off via the l-valine biosynthesis pathway.

Cryptococcus neoformans Ilv2p confers resistance to sulfometuron methyl and is required for survival at 37 °C and in vivo

Microbiology ◽  
2004 ◽  
Vol 150 (5) ◽  
pp. 1547-1558 ◽  
Author(s):  
Joanne M. Kingsbury ◽  
Zhonghui Yang ◽  
Tonya M. Ganous ◽  
Gary M. Cox ◽  
John H. McCusker
Keyword(s):  
Amino Acid ◽  
Cryptococcus Neoformans ◽  
Acetolactate Synthase ◽  
Gene Encoding ◽  
Sulfometuron Methyl ◽  
Branched Chain Amino Acid ◽  
Valine Biosynthesis ◽  
Branched Chain ◽  
Synthase Inhibitor

Acetolactate synthase catalyses the first common step in isoleucine and valine biosynthesis and is the target of several classes of inhibitors. The Cryptococcus neoformans ILV2 gene, encoding acetolactate synthase, was identified by complementation of a Saccharomyces cerevisiae ilv2 mutant. C. neoformans is highly resistant to the commercially available acetolactate synthase inhibitor, sulfometuron methyl (SM). Expression of C. neoformans ILV2 in S. cerevisiae conferred SM resistance, indicating that the SM resistance of C. neoformans is due, at least in part, to C. neoformans Ilv2p. The C. neoformans ILV2 gene was disrupted. The ilv2 mutants were auxotrophic for isoleucine and valine and the auxotrophy was satisfied by these amino acids only when proline, and not ammonium, was the nitrogen source, indicating nitrogen regulation of amino acid transport. ilv2 mutants rapidly lost viability at 37 °C and when starved for isoleucine and valine. Consistent with these phenotypes, an ilv2 mutant was avirulent and unable to survive in mice. Because C. neoformans Ilv2p is required for virulence and survival in vivo, inhibitors of branched-chain amino acid biosynthesis may make valuable antifungal agents.

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