Alternate requirement for pyridoxine or isoleucine in mutants of <i>Escherichia coli</i>

Grimminger, H.; Lingens, Franz

doi:10.1016/0014-5793(69)80338-8

Cited by 11 publications

(9 citation statements)

References 6 publications

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“…The existence of a class of pyridoxineless mutants which require either pyridoxine or glycolaldehyde for growth suggests that another type of pyridoxal phosphate "Km" mutant has been found. [This name applies to certain mutants of pyridoxal phosphate holoenzymes which respond with growth either to vitamin B6 or to the product of the respective biosynthetic pathway such as iso-cr_ 10 f5xl(y7M leucine (9), lysine (2), or serine (7).] But in this case, in contrast to the others, the mutants are unable to make any vitamin B, without glycolaldehyde being present.…”

Section: Discussionmentioning

confidence: 99%

Role of Vitamin B₆Biosynthetic Rate in the Study of Vitamin B₆Synthesis inEscherichia coli

Dempsey

1971

J Bacteriol

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Nutritional auxotrophs of Escherichia coli synthesize vitamin B 6 compounds at a rate of 1 × 10 −10 to 2 × 10 −10 moles per hr per mg (dry weight) of cells when they are suspended in minimal medium lacking their required nutrients. A few auxotrophs have been found to stop or reduce vitamin B 6 synthesis during such an experiment. These include thiamineless, citrate synthaseless, and pyridoxineless mutants as well as mutants which require four carbon compounds for growth. Glycolaldehyde was found to restore vitamin B 6 synthesis in the last named of these mutants without restoring normal growth. A class of pyridoxineless mutants which responded with normal growth to 0.4 m m glycolaldehyde or 0.15 × 10 −3 m m pyridoxol was also found. The results suggest that a thiamine pyrophosphate-requiring step as well as glycolaldehyde may be involved in pyridoxal phosphate biosynthesis.

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Section: Discussionmentioning

confidence: 99%

Role of Vitamin B₆Biosynthetic Rate in the Study of Vitamin B₆Synthesis inEscherichia coli

Dempsey

1971

J Bacteriol

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“…While this study was in progress, a short communication (8) described a group of Escherichia coli mutants which require either vitamin B., a-ketobutyrate, or isoleucine for growth. The authors concluded that these alternate requirements probably resulted from a mutational change in the biosynthetic threonine dehydratase such that its dissociation constant for pyridoxal-P was increased.…”

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confidence: 99%

Salmonella typhimurium Mutants with Alternate Requirements for Vitamin B ₆ or Isoleucine

1971

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Several mutants of Salmonella typhimurium LT-2, isolated as auxotrophs for vitamin B,,, grew without the added vitamin when supplied with either isoleucine, a-ketobutyrate, or a-keto-B-methylvalerate, but not with threonine or with other a-keto acids. When grown on minimal medium supplemented with isoleucine, these mutants synthesized vitamin B, in amounts comparable to wild-type cells; they thus appeared to contain a modified L-threonine dehydratase and to belong to genotype ilvA (threonine dehydratase) instead of pdx (pyridoxine). Direct assays confirmed this hypothesis. Wild-type cells (toluene-treated) showed approximately the same threonine dehydratase activity whether grown in the presence or absence of added pyridoxal-P; mutant cells approached the activity of wild-type cells only when they were grown with added vitamin B, and were assayed in the presence of pyridoxal-P. In cell-free extracts, the threonine dehydratase from mutant cells was cold labile and more labile to oxidative inactivation than the wild-type enzyme; furthermore, activation of the mutant apoenzyme required a 10to 20-fold higher concentration of pyridoxal-P than was required for the wild-type apoenzyme. These results show that cultures which appear auxotrophic for a given vitamin may synthesize that vitamin in normal amounts, the exogenous requirement arising from impaired binding of the vitamin-derived coenzyme to a genetically altered apoenzyme dependent on that coenzyme. Inadequate nutritional data to support the genetic findings can lead to erroneous genotype classification for such mutants.

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“…Firstly, the enzymatic defects in most pyridoxineless mutants have not been defined and therefore there cannot be at present a foolproof test that mutants classified phenotypically as Pdx are genotypically pdx. See, for example, the studies on "Km" mutants recently reported (10,11,13). Accordingly, the experiments were done with mutants from the three genetic classes which represent the majority of pdx mutants in E. coli B to establish the generality of the results.…”

Section: Resultsmentioning

confidence: 99%

Isoleucine and Threonine Can Prolong Protein and Ribonucleic Acid Synthesis in Pyridoxine-Starved Mutants of Escherichia coli B

Dempsey

Sims

1972

J Bacteriol

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Pyridoxineless mutants of Escherichia coli B stopped incorporation of nucleosides into trichloroacetic acid-insoluble material about 40 to 60 min after pyridoxine starvation was initiated, whereas incorporation of amino acids (measured the same way) slowed but did not stop for several hours. Both these incorporations and cell density were increased most effectively by the presence of either threonine or isoleucine. Arginine, glutamate, histidine, methionine, tryptophan, and tyrosine also caused significant but less dramatic increases. Inducibility of j3-galactosidase continued beyond the point where nucleic acids appeared to stop their synthesis, suggesting that messenger ribonucleic acid synthesis continued beyond ribosomal ribonucleic acid synthesis. This inducibility was also increased by isoleucine and threonine. The overall results suggest that the threonine-isoleucine biosynthetic pathway is the most sensitive to starvation for pyridoxine.

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Alternate requirement for pyridoxine or isoleucine in mutants of Escherichia coli

Cited by 11 publications

References 6 publications

Role of Vitamin B₆Biosynthetic Rate in the Study of Vitamin B₆Synthesis inEscherichia coli

Role of Vitamin B₆Biosynthetic Rate in the Study of Vitamin B₆Synthesis inEscherichia coli

Salmonella typhimurium Mutants with Alternate Requirements for Vitamin B ₆ or Isoleucine

Isoleucine and Threonine Can Prolong Protein and Ribonucleic Acid Synthesis in Pyridoxine-Starved Mutants of Escherichia coli B

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Alternate requirement for pyridoxine or isoleucine in mutants of Escherichia coli

Cited by 11 publications

References 6 publications

Role of Vitamin B6Biosynthetic Rate in the Study of Vitamin B6Synthesis inEscherichia coli

Role of Vitamin B6Biosynthetic Rate in the Study of Vitamin B6Synthesis inEscherichia coli

Salmonella typhimurium Mutants with Alternate Requirements for Vitamin B 6 or Isoleucine

Isoleucine and Threonine Can Prolong Protein and Ribonucleic Acid Synthesis in Pyridoxine-Starved Mutants of Escherichia coli B

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Role of Vitamin B₆Biosynthetic Rate in the Study of Vitamin B₆Synthesis inEscherichia coli

Role of Vitamin B₆Biosynthetic Rate in the Study of Vitamin B₆Synthesis inEscherichia coli

Salmonella typhimurium Mutants with Alternate Requirements for Vitamin B ₆ or Isoleucine