Three pathways of isoleucine biosynthesis in mutant strains of Saccharomyces cerevisiae

Vollbrecht, D.

doi:10.1016/0304-4165(74)90231-1

Cited by 18 publications

(14 citation statements)

References 9 publications

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“…Citramalate, in turn, is then converted to a-ketobutyrate. This ''citramalate pathway'' has not been conclusively demonstrated in plants and yeast, but data exist to support this possibility (Textor et al, 2007;Vollbrecht, 1974). Furthermore, detailed isotope labeling studies point to the possible existence of a novel pathway of fatty acid biosynthesis for sugar esters in members of the Solanaceae [e.g., tobacco (Nicotiana tabacum) and petunia (Petunia •hybrida)] led to the suggestion that some plants may possess CIM activity in specialized tissues (Kroumova and Wagner, 2003).…”

Section: Maturationmentioning

confidence: 99%

Changes in Free Amino Acid Content in ‘Jonagold’ Apple Fruit as Related to Branched-chain Ester Production, Ripening, and Senescence

Sugimoto¹,

Beaudry²

2011

J. Amer. Soc. Hort. Sci.

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The relationship among the free amino acid content, the expression of genes related to branched-chain amino acid metabolism {branched-chain aminotransferase [BCAT], α-keto acid decarboxylase [pyruvate decarboxylase (PDC)], and threonine deaminase [TD]}, and the production of branched-chain (BC) esters during ripening and senescence in ‘Jonagold’ apple fruit (Malus ×domestica) was studied. Eighteen amino acids were measured by liquid chromatography coupled with tandem mass spectrometry. The content for all amino acids changed with developmental stage and some shared similar patterns of accumulation/diminution. The pattern for isoleucine differed from all other amino acids, increasing more than 20-fold during the ripening process. The onset of the increase was concomitant with the onset of increasing ethylene and BC ester production and the content remained elevated even during senescence. The elevated isoleucine levels are consistent with an increase in the flux through the pathway leading to the formation and degradation of the isoleucine precursor α-keto-β-methylvalerate, which is used for production of BC esters containing 2-methylbutanol and 2-methylbutanoate moieties. Unexpectedly, the content of threonine, the amino acid from which isoleucine is thought to be derived in plants, did not change in concert with isoleucine, but rather declined somewhat after ripening was well underway. Patterns in the expression of some, but not all, of the putative BCAT and PDC genes appeared to reflect the rise and fall in ester formation; however, the expression of putative TD genes did not change during ripening. The patterns in gene expression and amino acid content are interpreted to suggest that the synthesis of α-keto-β-methylvalerate and isoleucine during apple ripening may depend on an as yet uncharacterized pathway that bypasses threonine, similar to the citramalate pathway found in some bacteria.

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Section: Maturationmentioning

confidence: 99%

Changes in Free Amino Acid Content in ‘Jonagold’ Apple Fruit as Related to Branched-chain Ester Production, Ripening, and Senescence

Sugimoto¹,

Beaudry²

2011

J. Amer. Soc. Hort. Sci.

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“…Some anaerobes can assimilate 2-methylbutyrate into isoleucine (33). In some pseudorevertants of ilvA mutants, ␣-ketobutyrate can arise from precursors other than threonine (3,6,9,11,13,14,15,30,39,41). Of the latter, the most commonly observed was a route from pyruvate and acetyl coenzyme A (acetyl-CoA) via citramalate (3,9,39,41).…”

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confidence: 99%

“…In some pseudorevertants of ilvA mutants, ␣-ketobutyrate can arise from precursors other than threonine (3,6,9,11,13,14,15,30,39,41). Of the latter, the most commonly observed was a route from pyruvate and acetyl coenzyme A (acetyl-CoA) via citramalate (3,9,39,41). This "pyruvate pathway" was initially proposed for the genus Leptospira (9,41) because isotope-labeling experiments indicated that in some leptospiral strains, ␣-ketobutyrate was derived from pyruvate rather than threonine.…”

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confidence: 99%

Isoleucine Biosynthesis in Leptospira interrogans Serotype lai Strain 56601 Proceeds via a Threonine-Independent Pathway

Zhang

Guo

et al. 2004

J Bacteriol

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Three leuA-like protein-coding sequences were identified in Leptospira interrogans. One of these, the cimA gene, was shown to encode citramalate synthase (EC 4.1.3.-). The other two encoded ␣-isopropylmalate synthase (EC 4.1.3.12). Expressed in Escherichia coli, the citramalate synthase was purified and characterized. Although its activity was relatively low, it was strictly specific for pyruvate as the keto acid substrate. Unlike the citramalate synthase of the thermophile Methanococcus jannaschii, the L. interrogans enzyme is temperature sensitive but exhibits a much lower K m (0.04 mM) for pyruvate. The reaction product was characterized as (R)-citramalate, and the proposed ␤-methyl-D-malate pathway was further confirmed by demonstrating that citraconate was the substrate for the following reaction. This alternative pathway for isoleucine biosynthesis from pyruvate was analyzed both in vitro by assays of leptospiral isopropylmalate isomerase (EC 4.2.1.33) and ␤-isopropylmalate dehydrogenase (EC 1.1.1.85) in E. coli extracts bearing the corresponding clones and in vivo by complementation of E. coli ilvA, leuC/D, and leuB mutants. Thus, the existence of a leucine-like pathway for isoleucine biosynthesis in L. interrogans under physiological conditions was unequivocally proven. Significant variations in either the enzymatic activities or mRNA levels of the cimA and leuA genes were detected in L. interrogans grown on minimal medium supplemented with different levels of the corresponding amino acids or in cells grown on serum-containing rich medium. The similarity of this metabolic pathway in leptospires and archaea is consistent with the evolutionarily primitive status of the eubacterial spirochetes.

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“…a-Ketobutyrate can be derived from homoserine (Flavin & Segal, 1964), from glutamate via @-methylaspartate (Phillips et al, 1972), from pyruvate by chain elongation (Vollbrecht, 1974;Charon et al, 1974;Westfall et al, 1983;Kisumi et al, 1977), and from propionate by carboxylation (Sauer et al, 1975;Buchanan, 1969). In some cases, when there is an abundance of volatile fatty acids in the medium, 2-methylbutyrate can be carboxylated directly to isoleucine by some anaerobic bacteria from the rumen (Robinson & Allison, 1969).…”

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Biosynthesis of isoleucine in methanogenic bacteria: a carbon-13 NMR study

Ekiel¹,

Smith²,

Sprott³

1984

Biochemistry

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The biosynthesis of isoleucine by seven species of methanogenic bacteria was studied by using 13C NMR, following growth in media containing specifically 13C-labeled compounds. It was found that in these bacteria a-ketobutyrate is not derived from threonine. In all cases, when acetate and C 0 2 serve as the total carbon sources, the labeling pattern of isoleucine is consistent with the operation of the pyruvate Published 1984 by the American Chemical Society Crit. Rev. Environ. Control 4 , 131-191. 1195-1203. 932-94 1. chem. (Tokyo) 82, 95-103. J . 99, 76-86. J . Bacteriol. 109, 714-719. 1220-1226. J . 150, 357-372. Chem. SOC. 96, 4694-4696. 98 2-9 86.

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Three pathways of isoleucine biosynthesis in mutant strains of Saccharomyces cerevisiae

Cited by 18 publications

References 9 publications

Changes in Free Amino Acid Content in ‘Jonagold’ Apple Fruit as Related to Branched-chain Ester Production, Ripening, and Senescence

Changes in Free Amino Acid Content in ‘Jonagold’ Apple Fruit as Related to Branched-chain Ester Production, Ripening, and Senescence

Isoleucine Biosynthesis in Leptospira interrogans Serotype lai Strain 56601 Proceeds via a Threonine-Independent Pathway

Biosynthesis of isoleucine in methanogenic bacteria: a carbon-13 NMR study

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