Radiosensitivity of Escherichia coli 15T - and the Metabolic Effect of Cysteine

Nagy, Z.; Hernádi, F.; Kovács, P.; Valyi-Nagy, T

doi:10.2307/3572522

Cited by 10 publications

(2 citation statements)

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“…Although cysteine inhibition of S. mutans, and probably of S. salivarius, appears to involve an inhibition of branched-chain amino acid synthesis, the branched-chain amino acids did not completely eliminate the cysteine inhibition of S. mutans under certain growth conditions (see Table 5). Cysteine has also been shown to inhibit RNA synthesis (15,18) as well as branchedchain amino acid synthesis in E. coli (13,16), and it has been suggested these metabolic alterations may result in "unbalanced growth" of this organism (18). Furthermore, at cysteine concentrations above 2.0 mM, an additional secondary inhibitory effect of cysteine, involving an interaction with membrane-bound respiratory enzymes, may lead to energy depletion of the cells (15).…”

Section: Discussionmentioning

confidence: 99%

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Cysteine toxicity for oral streptococci and effect of branched-chain amino acids

Cowman¹,

Baron²,

Fitzgerald³

1983

Infect Immun

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Cysteine was bactericidal to strains of Streptococcus mutans and S. salivarius in concentrations that were nontoxic to S. sanguis, S. milleri, or S. mitior when these microorganisms were incubated in a saliva protein-based synthetic medium. Cysteine toxicity for S. mutans also occurred after incubation in synthetic base medium supplemented with amino acids as the nitrogen source for growth. The bactericidal effect of cysteine for S. mutans or S. salivarius in the saliva protein medium was influenced by the cysteine oxidative activity associated with the saliva protein fraction. Valine alone or in combination with leucine or isoleucine was effective in overcoming cysteine toxicity for susceptible strains of S. mutans or S. salivarius. Cysteine toxicity for these oral streptococci may be due to cysteine inhibition of an enzymatic step in the valine-leucine biosynthetic pathway.

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Section: Discussionmentioning

confidence: 99%

“…Although cysteine has been reported to be toxic for a number of microorganisms and fungi (2,3,12,13,15,16,18,23), different mechanisms of inhibition account for its toxicity. For example, cysteine toxicity for Escherichia coli has been shown to be due to a cysteine-specific inhibition of branched-chain amino acid synthesis (13, 15,16).…”

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confidence: 99%