Genetic and Biochemical Studies of Partially Active Tryptophan Synthetase Mutants of
            <i>Saccharomyces cerevisiae</i>

Manney, Thomas R.; Duntze, W.; Janosko, Nancy; Salazar, Jorge Soria

doi:10.1128/jb.99.2.590-596.1969

Cited by 25 publications

(3 citation statements)

References 20 publications

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“…Radford has also detected a pattern of polarized complementation which suggests a reading of a single messenger from CPSpyr to ATC. A similar situation with respect to a bifunctional protein is seen in tryptophan synthetase of yeast (19,20).…”

Section: Utp (5 X 1o-m)mentioning

confidence: 62%

Pyrimidine-Specific Carbamyl Phosphate Synthetase in Neurospora crassa

Williams

Davis

1970

J Bacteriol

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Two carbamyl phosphate synthetases, the first an arginine-synthetic enzyme (CPSarg) and the second a pyrimidine-synthetic enzyme (CPSpyr), are shown to be present in Neurospora. The two enzymes can be separated on the basis of size and are distinguished by several different properties. Both CPSpyr and CPS.rR have substrate requirements of adenosine triphosphate, HC03-, and L-glutamine, although NH4+ in high concentration will partially replace glutamine. CPSpyr activity can be completely inhibited by 5 X 104 to 10 X 10-4 M uridine triphosphate (UTP). CPSpyr is cold-labile and can be protected against cold inactivation by UTP. The synthesis of CPSpyr and aspartate transcarbamylase (ATC), the initial enzymatic steps of the pyrimidine pathway, are co-derepressed by pyrimidine starvation. Mutations affecting CPSpyr and ATC all map at the same locus, pyr-3. Three classes of mutants with respect to the two activities were found: CPS+ATC-, CPS-ATC+, and CPS-ATC-. The distribution of these mutants on the genetic map, together with other data, indicate that the two activities are carried by a bifunctional protein.

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Section: Utp (5 X 1o-m)mentioning

confidence: 62%

Pyrimidine-Specific Carbamyl Phosphate Synthetase in Neurospora crassa

Williams

Davis

1970

J Bacteriol

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“…t7p3B, trp3C; see 23) and tryptophan synthase (trp5A, trp5B; see 19). All of the auxotrophs used in this study were nonleaky and had a very low reversion rate.…”

Section: Methodsmentioning

confidence: 99%

“…Products of the two genes, trp2 and trp3, form an aggregate which catalyzes the first and fourth steps of the pathway (23). Tryptophan synthase, which catalyzes the last step of the pathway, is coded for by a single gene (6), but it is possible to obtain mutants that either excrete or utilize indole (19).…”

mentioning

confidence: 99%

Tryptophan biosynthesis in Saccharomyces cerevisiae: control of the flux through the pathway

Miozzari¹,

Niederberger²,

Hütter³

1978

J Bacteriol

184

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Enzyme derepression and feedback inhibition of the first enzyme are the regulatory mechanisms demonstrated for the tryptophan pathway in Saccharomyces cerevisiae. The relative contributions of the two mechanisms to the control of the flux through the pathway in vivo were analyzed by (i) measuring feedback inhibition of anthranilate synthase in vivo, (ii) determining the effect of regulatory mutations on the level of the tryptophan pool and the flux through the pathway, and (iii) varying the gene dose of individual enzymes of the pathway at the tetraploid level. We conclude that the flux through the pathway is adjusted to the rate of protein synthesis by means of feedback inhibition of the first enzyme by the end product, tryptophan. The synthesis of the tryptophan enzymes could not be repressed below a basal level by tryptophan supplementation of the media. The enzymes are present in excess. Increasing or lowering the concentration of individual enzymes had no noticeable influencing on the overall flux to tryptophan. The uninhibited capacity of the pathway could be observed both upon relieving feedback inhibition by tryptophan limitation and in feedback-insensitive mutants. It exceeded the rate of consumption of the amino acid on minimal medium by a factor of three. Tryptophan limitation caused derepression of four of the five tryptophan enzymes and, as a consequence, led to a further increase in the capacity of the pathway. However, because of the large reserve capacity of the "repressed" pathway, tryptophan limitation could not be imposed on wild-type cells without resorting to the use of analogs. Our results, therefore, suggest that derepression does not serve as an instrument for the specific regulation of the flux through the tryptophan pathway.

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Mutation Induction in Yeast

Mortimer

Manney

1971

Chemical Mutagens

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Genetic and Biochemical Studies of Partially Active Tryptophan Synthetase Mutants of Saccharomyces cerevisiae

Cited by 25 publications

References 20 publications

Pyrimidine-Specific Carbamyl Phosphate Synthetase in Neurospora crassa

Pyrimidine-Specific Carbamyl Phosphate Synthetase in Neurospora crassa

Tryptophan biosynthesis in Saccharomyces cerevisiae: control of the flux through the pathway

Mutation Induction in Yeast

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