The role of amino acids in the regulation of hydrogen sulfide production during ultradian respiratory oscillation of Saccharomyces cerevisiae

Abstract

We previously demonstrated that periodic H2S production during aerobic continuous culture of Saccharomyces cerevisiae resulted in ultradian respiratory oscillation, and that H2S production was dependent on the activity of sulfate uptake and the level of sulfite. To investigate the mechanism of regulation of the sulfate assimilation pathway and of respiratory oscillation, several amino acids were pulse-injected into cultures during respiratory oscillation. Injection of sulfur amino acids or their derivatives perturbed respiratory oscillation, with changes in the H2S production profile. Four major regulators of H2S production in the sulfate assimilation pathway and respiratory oscillation were identified: (1) O-acetylhomoserine, not O-acetylserine, as a sulfide acceptor, (2) homoserine/threonine as a regulator of O-acetylhomoserine supply, (3) methionine/S-adenosyl methionine as a negative regulator of sulfate assimilation, and (4) cysteine (or its derivatives) as an essential regulator. The results obtained after the addition of DL-propargylglycine (5 microM and 100 microM) and cystathionine (50 microM) suggested that the intracellular cysteine level and cystathionine gamma-lyase, rather than methionine/S-adenosylmethionine, play an essential role in the regulation of sulfate assimilation and respiratory oscillation. Based on these results and those of our previous reports, we propose that periodic depletion of cysteine (or its derivatives), which is involved in the detoxification of toxic materials originating from respiration, causes periodic H2S production.

Regulation of yeast oscillatory dynamics

“…The block relaxes when the intracellular concentration of amino acids decreases; therefore, the observed oscillation in intracellular amino acid concentrations creates a strong feedback on this transcriptional regulation circuitry. The activation of GCN4 translation was not the result of amino acids in the feed media becoming limited because extracellular amino acids were always below the limits of detection, and ammonia was always available for biosynthesis (25). Furthermore, addition of glutamate, cysteine, and threonine causes dose-dependent inhibition of respiration and growth (7,26,27), which is the opposite of what may be expected if the cell were limited by amino acids.…”

“…The metabolite data set used previous work (5,7,12,21,22,25,27,28,37,38), and GC-MS analyses (SI Methods) of intracellular metabolites were used to construct the metabolite data set. All Western blots were carried out according to the manufacturer's instructions (Atto, Bunkyo-ku, Tokyo, Japan).…”

Antecedent hydrogen sulfide elicits an anti-inflammatory phenotype in postischemic murine small intestine: role of heme oxygenase-1

“…H 2 S also exerts antioxidant effects and limits oxidative stress by virtue of its actions to raise intracellular glutathione levels by enhancing the activity of ␥-glutamylcysteine synthetase and upregulating cysteine transport (17). H 2 S also enhances the ability of superoxide dismutase to scavenge superoxide (27). Furthermore, H 2 S reduces apoptosis by inhibition of caspase-3 cleavage and p38 MAPK phosphorylation (24), which may contribute to potential infarct-sparing effects in I/R.…”

Relative Contributions of Cystathionine β-Synthase and γ-Cystathionase to H2S Biogenesis via Alternative Trans-sulfuration Reactions

“…10 (30), to achieve population synchronization. Interestingly, the H 2 S producing sulfate assimilation pathway and respiratory oscillations have been linked to the trans-sulfuration pathway with intracellular cysteine levels and CSE playing a regulatory role (31).…”

“…The turnover number of this reaction under V max conditions (25.5 s Ϫ1 ) is ϳ2-fold lower than for the condensation of cysteine and homocysteine (reaction 4, 55.0 s Ϫ1 ), leading to H 2 S production ( Table 1). Yeast maintains very low cysteine concentration (0.25-0.45 M), which is ϳ1-10% of the intracellular concentration of other amino acids in this organism (4,31). Hence, at intracellular levels of cysteine and serine, reaction 1 is expected to dominate over reaction 4.…”