l-Alanine as an end product of glycolysis inSaccharomyces cerevisiae growing under different hypoxic conditions

Chico, E.; Olavarría, J S; Castro, Ignacio Núñez de

doi:10.1007/bf00643222

Cited by 12 publications

(6 citation statements)

References 15 publications

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“…The presence of at least two alanine aminotransferase isozymes is widely distributed in animals, plants, yeasts and bacteria. In these systems, ALT isozymes have been considered to constitute the main pathway leading to alanine biosynthesis and catabolism [1]–[6]. Alanine catabolic and anabolic pathways are central in nitrogen and carbon metabolic networks.…”

Section: Introductionmentioning

confidence: 99%

Paralogous ALT1 and ALT2 Retention and Diversification Have Generated Catalytically Active and Inactive Aminotransferases in Saccharomyces cerevisiae

et al. 2012

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BackgroundGene duplication and the subsequent divergence of paralogous pairs play a central role in the evolution of novel gene functions. S. cerevisiae possesses two paralogous genes (ALT1/ALT2) which presumably encode alanine aminotransferases. It has been previously shown that Alt1 encodes an alanine aminotransferase, involved in alanine metabolism; however the physiological role of Alt2 is not known. Here we investigate whether ALT2 encodes an active alanine aminotransferase.Principal FindingsOur results show that although ALT1 and ALT2 encode 65% identical proteins, only Alt1 displays alanine aminotransferase activity; in contrast ALT2 encodes a catalytically inert protein. ALT1 and ALT2 expression is modulated by Nrg1 and by the intracellular alanine pool. ALT1 is alanine-induced showing a regulatory profile of a gene encoding an enzyme involved in amino acid catabolism, in agreement with the fact that Alt1 is the sole pathway for alanine catabolism present in S. cerevisiae. Conversely, ALT2 expression is alanine-repressed, indicating a role in alanine biosynthesis, although the encoded-protein has no alanine aminotransferase enzymatic activity. In the ancestral-like yeast L. kluyveri, the alanine aminotransferase activity was higher in the presence of alanine than in the presence of ammonium, suggesting that as for ALT1, LkALT1 expression could be alanine-induced. ALT2 retention poses the questions of whether the encoded protein plays a particular function, and if this function was present in the ancestral gene. It could be hypotesized that ALT2 diverged after duplication, through neo-functionalization or that ALT2 function was present in the ancestral gene, with a yet undiscovered function.Conclusions ALT1 and ALT2 divergence has resulted in delegation of alanine aminotransferase activity to Alt1. These genes display opposed regulatory profiles: ALT1 is alanine-induced, while ALT2 is alanine repressed. Both genes are negatively regulated by the Nrg1 repressor. Presented results indicate that alanine could act as ALT2 Nrg1-co-repressor.

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Section: Introductionmentioning

confidence: 99%

Paralogous ALT1 and ALT2 Retention and Diversification Have Generated Catalytically Active and Inactive Aminotransferases in Saccharomyces cerevisiae

et al. 2012

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“…Specifically, in response to hypoxia, mammalian culture cells produce increased amounts of amino acids, fatty acids, and phospholipids, in addition to lactate (4,21), whereas Saccharomyces cerevisiae cells produce increased amounts of ethanol, glycerol, succinate, and alanine (22,23) as the end products of glycolysis. The production of pyruvate, which is associated with the synthetic pathways of fatty acids, nucleotides, and other amino acids (24), is necessary for cell growth under hypoxia.…”

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confidence: 99%

Spatial Reorganization of Saccharomyces cerevisiae Enolase To Alter Carbon Metabolism under Hypoxia

et al. 2013

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c Hypoxia has critical effects on the physiology of organisms. In the yeast Saccharomyces cerevisiae, glycolytic enzymes, including enolase (Eno2p), formed cellular foci under hypoxia. Here, we investigated the regulation and biological functions of these foci. Focus formation by Eno2p was inhibited temperature independently by the addition of cycloheximide or rapamycin or by the single substitution of alanine for the Val22 residue. Using mitochondrial inhibitors and an antioxidant, mitochondrial reactive oxygen species (ROS) production was shown to participate in focus formation. Focus formation was also inhibited temperature dependently by an SNF1 knockout mutation. Interestingly, the foci were observed in the cell even after reoxygenation. The metabolic turnover analysis revealed that [U-13 C]glucose conversion to pyruvate and oxaloacetate was accelerated in focus-forming cells. These results suggest that under hypoxia, S. cerevisiae cells sense mitochondrial ROS and, by the involvement of SNF1/ AMPK, spatially reorganize metabolic enzymes in the cytosol via de novo protein synthesis, which subsequently increases carbon metabolism. The mechanism may be important for yeast cells under hypoxia, to quickly provide both energy and substrates for the biosynthesis of lipids and proteins independently of the tricarboxylic acid (TCA) cycle and also to fit changing environments.

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“…Alanine aminotransferases catalyse reversible transamination between alanine and α-ketoglutarate, leading to pyruvate and glutamate. At least two alanine aminotransferase isozymes, generated through independent gene duplication events, occur frequently in animals, plants, yeasts and bacteria, and are proposed to be involved in the main pathways of both alanine biosynthesis and catabolism [15,[54][55][56][57][58]. Amino acid metabolism has been thoroughly studied in S. cerevisiae; however, no alanine auxotrophs have been isolated from this yeast.…”

Section: Modelling Of the Nrg1/rtg3 Complex The Unicity Of Nrg1mentioning

confidence: 99%

“…ALT1 and ALT2 encode proteins with 65% identity and are assumed to be paralogous alanine transaminases [ 15 ]. Additional phylogenetic studies suggested that ALT1 and ALT2 originated in one of the two distinct parental strains, which gave rise to the ancestral hybrid [ 16 ].…”

Section: Introductionmentioning

confidence: 99%

Neo-functionalization in Saccharomyces cerevisiae : a novel Nrg1-Rtg3 chimeric transcriptional modulator is essential to maintain mitochondrial DNA integrity

Campero-Basaldua,

González,

García

et al. 2023

R. Soc. open sci.

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In Saccharomyces cerevisiae, the transcriptional repressor Nrg1 (Negative Regulator of Glucose-repressed genes) and the β-Zip transcription factor Rtg3 (ReTroGrade regulation) mediate glucose repression and signalling from the mitochondria to the nucleus, respectively. Here, we show a novel function of these two proteins, in which alanine promotes the formation of a chimeric Nrg1/Rtg3 regulator that represses the ALT2 gene (encoding an alanine transaminase paralog of unknown function). An NRG1/NRG2 paralogous pair, resulting from a post-wide genome small-scale duplication event, is present in the Saccharomyces genus. Neo-functionalization of only one paralog resulted in the ability of Nrg1 to interact with Rtg3. Both nrg1 Δ and rtg3 Δ single mutant strains were unable to use ethanol and showed a typical petite (small) phenotype on glucose. Neither of the wild-type genes complemented the petite phenotype, suggesting irreversible mitochondrial DNA damage in these mutants. Neither nrg1 Δ nor rtg3 Δ mutant strains expressed genes encoded by any of the five polycistronic units transcribed from mitochondrial DNA in S. cerevisiae . This, and the direct measurement of the mitochondrial DNA gene complement, confirmed that irreversible damage of the mitochondrial DNA occurred in both mutant strains, which is consistent with the essential role of the chimeric Nrg1/Rtg3 regulator in mitochondrial DNA maintenance.

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l-Alanine as an end product of glycolysis inSaccharomyces cerevisiae growing under different hypoxic conditions

Cited by 12 publications

References 15 publications

Paralogous ALT1 and ALT2 Retention and Diversification Have Generated Catalytically Active and Inactive Aminotransferases in Saccharomyces cerevisiae

Paralogous ALT1 and ALT2 Retention and Diversification Have Generated Catalytically Active and Inactive Aminotransferases in Saccharomyces cerevisiae

Spatial Reorganization of Saccharomyces cerevisiae Enolase To Alter Carbon Metabolism under Hypoxia

Neo-functionalization in Saccharomyces cerevisiae : a novel Nrg1-Rtg3 chimeric transcriptional modulator is essential to maintain mitochondrial DNA integrity

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