Mutants in the biosynthesis of isoleucine in a non-mating, non-sporulating brewing strain of Saccharomyces carlsbergensis

Kielland‐Brandt, Morten C.; Petersen, J.; Mikkelsen, Jørn Dalgaard

doi:10.1007/bf02910869

Cited by 23 publications

(7 citation statements)

References 14 publications

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“…AI1 the reactions downstream from TD are catalyzed by enzymes that are shared by the two main branches of the biosynthetic pathway that lead to the production of the branched-chain amino acids Ile, Leu, and Val. In bacteria and yeast, resistance to the Ile structural analog thiaIle was associated with a loss of feedback sensitivity of TD to Ile (Umbarger, 1971;Kielland-Brandt et al, 1979). In Rosa cells, resistance to the Ile structural analog OMT was also associated with a TD that had reduced sensitivity to feedback inhibition by Ile (Strauss et al, 1985).…”

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confidence: 99%

L-O-Methylthreonine-Resistant Mutant of Arabidopsis Defective in Isoleucine Feedback Regulation

Mourad

King

1995

Plant Physiol.

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Threonine dehydratase/deaminase (TD), the first enzyme in the isoleucine biosynthetic pathway, is feedback inhibited by isoleucine. By screening M, populations of ethyl methane sulfonatetreated Arabidopsis thaliana Columbia wild-type seeds, we isolated five independent mutants that were resistant to i-O-methylthreonine, an isoleucine structural analog. Crowth in the mutants was 50-to 600-fold more resistant to i-Omethylthreonine than in the wild type. l h e resistance was dueto a single, dominant nuclear gene that was denoted omrl and was mapped to chromosome 3 in CM11 b, the mutant line exhibiting the highest level of resistance. Biochemical characteristics (specific activities, K, , V,,,, and pH optimum) of TD in extracts from the wild type and C M l l b were similar except for the inhibition constant of isoleucine, which was 50-fold higher in C M l l b than in the wild type. Levels of free isoleucine were 20-fold higher in extracts from C M l l b than in extracts from wild type. Therefore, isoleucine feedback insensitivity in G M l l b is due to a mutant form of the TD enzyme encoded by omrl. l h e mutant allele Omrl of the line C M l l b could provide a new selectable marker for plant genetic transformation.TD, the first enzyme in the biosynthetic pathway of Ile, catalyzes the formation of 2-oxobutyrate from Thr in a two-step reaction. The first step is a dehydration of Thr followed by rehydration and liberation of ammonia (Bryan, 1990). AI1 the reactions downstream from TD are catalyzed by enzymes that are shared by the two main branches of the biosynthetic pathway that lead to the production of the branched-chain amino acids Ile, Leu, and Val. In bacteria and yeast, resistance to the Ile structural analog thiaIle was associated with a loss of feedback sensitivity of TD to Ile (Umbarger, 1971;Kielland-Brandt et al., 1979). In Rosa cells, resistance to the Ile structural analog OMT was also associated with a TD that had reduced sensitivity to feedback inhibition by Ile (Strauss et al., 1985). Being in tissue culture and having high ploidy level, it was not possible to determine the genetic basis of feedback insensitivity to Ile in the Rasa variant, the only plant mutant with an Ile-insensitive TD.We are isolating and characterizing mutants of the branched-chain amino acid biosynthetic pathway at the ' This work was supported by research grants from the Natural MATERIALS A N D METHODS Seed MutagenesisAbout 100,000 seeds of Arabidopsis tkaliana (L.) Heynh Columbia wild type were allowed to imbibe (v/v) in an aqueous solution of 0.2% EMS for 18 h at room temperature. The mutagenized seed (M,) was washed severa1 times with distilled water, planted in subpopulations, and allowed to self-fertilize to produce M, seed. The M, seed were harvested from each subpopulation separately, surface sterilized, and planted on agar-solidified medium containing 0.5 mM OMT. In this medium wild-type seedlings were completely bleached and died immediately after germination, whereas resistant mutants were able to germinate and prod...

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L-O-Methylthreonine-Resistant Mutant of Arabidopsis Defective in Isoleucine Feedback Regulation

Mourad

King

1995

Plant Physiol.

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“…In fact, the first push toward engineering the production of pentanols in microorganisms came about by exploiting this biosynthetic pathway. By using mutagenesis and selection based on the biosynthetic amino acid pathways, several groups have been able to increase higher alcohol formation in yeast (Kielland-Brandt et al 1979; Fukuda et al 1993; Suzzi et al 1998). By using the toxicity of chemical analogues of the amino acids isoleucine and leucine as selection pressure, they were able to augment production of 2-methyl-1-butanol and 3-methyl-1-butanol, respectively, during fermentation.…”

Section: Natural Production Of Pentanolsmentioning

confidence: 99%

Pentanol isomer synthesis in engineered microorganisms

Cann

Liao

2009

Appl Microbiol Biotechnol

125

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Pentanol isomers such as 2-methyl-1-butanol and 3-methyl-1-butanol are a useful class of chemicals with a potential application as biofuels. They are found as natural by-products of microbial fermentations from amino acid substrates. However, the production titer and yield of the natural processes are too low to be considered for practical applications. Through metabolic engineering, microbial strains for the production of these isomers have been developed, as well as that for 1-pentanol and pentenol. Although the current production levels are still too low for immediate industrial applications, the approach holds significant promise for major breakthroughs in production efficiency.

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“…The initial result of such a cross gives a high yield of progeny \\lith the nuclear genotype of one S. L. STURLEY AND T. W. YOUNG parent and the cytoplasmic elements of both parents: thus, hybrids containing the mitochondrial genome of one parent and the nuclear complement of the other have been constructed (Conde-Zurita and Mascourt-Suarez, 1981). This phenomenon of cytoduction has also been used to transfer other cytoplasmic elements, such as the 2 J..l.ffi plasmid (Livingston, 1977) and its derivatives (Kielland-Brandt et al, 1979) as well as to confer anticontaminant properties on commercial strains by the transfer of the double-stranded RNA, killer factor (Ouchi et al, 1979;Young, 1981) (Figure 2). This plasmid encodes the production of, and immunity to, a toxin known to kill many wild yeasts.…”

Section: Mutation Selectionmentioning

confidence: 99%