Threonine Inhibition in a Strain of Neurospora

Doudney, C. O.; Wagner, Robert P.

doi:10.1073/pnas.38.3.196

Cited by 20 publications

(7 citation statements)

References 8 publications

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“…A similar threonine-methionine antagonism has been observed by Doudney and Wagner (1952) in a Neurospora mutant, strain T-77. However, the mechanism of this effect has not been clarified.…”

Section: Discussionsupporting

confidence: 50%

Derepression of valine-sensitive acetohydroxy acid synthase by threonine, .ALPHA.-ketobutyrate or isoleucine in Escherichia coli K12.

Okada

1982

The Japanese journal of genetics

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After nutritional shift-down, threonine, a-ketobutyrate, or isoleucine within certain concentration range stimulated derepression of the synthesis of acetohydroxy acid synthase in strain W3110-215, a low-thymine requiring derivative of Escherichia coli K12. The acetohydroxy acid synthase induced by isoleucine was valine-sensitive.Since chloramphenicol inhibited the increase of the enzyme activity, the increase seemed to be due to enhancement of enzyme synthesis and not to the activation of the enzyme. From these results, it was suggested that not only limitation of leucine or valine, but also the presence of excess threonine or isoleucine is necessary for efficient derepression of the synthesis of acetohydroxy acid synthase.On the other hand, threonine did not stimulate the derepression of the synthesis of the enzyme in strains W2252 and 58-161, methionine-auxotrophic mutants of E. coli K12, growing in minimal medium containing methionine. When a prototrophic strain with regard to methionine requirement was used, methionine or threonine added in minimal medium derepressed synthesis of acetohydroxy acid synthase, but the simultaneous addition of the two compounds did not give any synergistic effect on the enzyme synthesis. The mechanisms of these phenomena are unknown.

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“…A similar threonine-methionine antagonism has been observed by Doudney and Wagner (1952) in a Neurospora mutant, strain T-77. However, the mechanism of this effect has not been clarified.…”

Section: Discussionsupporting

confidence: 50%

Derepression of valine-sensitive acetohydroxy acid synthase by threonine, .ALPHA.-ketobutyrate or isoleucine in Escherichia coli K12.

Okada

1982

The Japanese journal of genetics

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“…Therefore, any additional stress cannot be overcome. Other investigators have also observed the inhibition of bradytrophs by normal metabolites (8,9,21,24).…”

Section: Discussionmentioning

confidence: 84%

Cross Pathway Regulation: Effect of Histidine on the Synthesis and Activity of Enzymes of Aromatic Acid Biosynthesis in Bacillus subtilis

Nester

1968

J Bacteriol

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L-Histidine and, to a lesser degree, L-phenylalanine at concentrations of 10-i M inhibit the growth of leaky mutants (bradytrophs) of Bacillus subtilis that are deficient in the synthesis of p-hydroxyphenylpyruvate, the first intermediate specific to tyrosine synthesis. The inhibition can be overcome by growth factor amounts of L-tyrosine and p-hydroxyphenylpyruvate. Histidine and phenylalanine are capable of inhibiting the synthesis of tyrosine in several ways, and the major physiological effect which results in growth inhibition has not been established. Both L-histidine and L-phenylalanine inhibit the activity of prephenate dehydrogenase at concentrations about 100-fold higher than the inhibitory concentration of L-tyrosine. Histidine also appears to repress the synthesis of prephenate dehydrogenase because a histidine bradytroph growing in histidine-supplemented medium has a twofold lower level of this enzyme than the same cells growing in unsupplemented medium. These same two amino acids also inhibit the growth of a bradytroph deficient in dehydroquinate synthetase, an early enzyme in the pathway of tyrosine, phenylalanine, and tryptophan synthesis. The inhibition is overcome by a combination of tyrosine and phenylalanine. Histidine-resistant derivatives of both the prephenate dehydrogenase and dehydroquinate synthetase-deficient strains, which simultaneoulsy have gained resistance to phenylalanine, have been isolated. Most of these resistant mutants synthesize additional tyrosine compared with the parent strain. One class of resistant mutants excretes tyrosine and has a number of enzymes of aromatic acid synthesis which are no longer repressible by any combination of the aromatic amino acids. Tyrosine inhibits the growth of histidine bradytrophs. Histidine, at growth factor levels, overcomes the inhibition.

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“…(67) have obtained evidence that a number of mutants of the tryptophan nicotinic acid group are not completely devoid of the capacity to carry out the synthesis; 7 out of 9 strains tested showed evidence of incomplete blocking. Doudncy & Wagner (68), on the basis of study of a thrconine-sensitive mutant, have arrived at the interesting concluslon that threonlne and homocystcinc may bc prccursors of the thiazole moiety of thiamine. Haas el c~.…”

Section: Metabolic Pathwaysmentioning

confidence: 99%