• Journal of Life Science
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• v.28 no.8
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• pp.985-991
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• 2018

Biological clocks are the basis of temporal control of metabolism and behavior. These clocks are characterized by autonomous free-running oscillation and temperature compensation and are found in animals, plants, and microorganisms. To date, various biological clocks have been reported. These include clocks governing hibernation, sleep/wake, heartbeat, and courtship song. These clocks can be differentiated by the period of rhythms, for example, infradian rhythms (> 24-hr period), circadian rhythms (24-hr period), and ultradian rhythms (< 24-hr period). In yeast (Saccharomyces cerevisiae), at least five different autonomous oscillations have been reported; (1) glycolytic oscillations (T = 1~30 min), (2) cell cycle-dependent oscillations (T = 2~16 hr), (3) ultradian metabolic oscillations (T = 15~50 min), (4) yeast colony oscillations (T = a few hours), and (5) circadian oscillations (T = 24 hr). In this review, we discuss studies on oscillators, pacemakers, and synchronizers, in addition to the application of biological clocks, to demonstrate the nature of autonomous oscillations, especially ultradian metabolic oscillations of S. cerevisiae.

• Journal of Microbiology
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• v.43 no.4
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• pp.375-380
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• 2005

Autonomous ultradian metabolic oscillation (T$\simeq$50 min) was detected in an aerobic chemostat culture of Saccharomyces cerevisiae. A pulse injection of GSH (a reduced form of glutathione) into the culture induced a perturbation in metabolic oscillation, with respiratory inhibition caused by $H_2S$ burst pro-duction. As the production of $H_2S$ in the culture was controlled by different amino acids, we attempted to characterize the effects of GSH on amino acid metabolism, particularly with regard to branched chain and sulfur-containing amino acids. During stable metabolic oscillation, concentrations of intra-cellular glutamate, aspartate, threonine, valine, leucine, isoleucine, and cysteine were observed to oscil-late with the same periods of dissolved $O_2$ oscillation, although the oscillation amplitudes and maximal phases were shown to differ. The methionine concentration was stably maintained at 0.05 mM. When GSH (100 $\mu$M) was injected into the culture, cellular levels of branched chain amino acids increased dramatically with continuous $H_2S$production, whereas the cysteine and methionine concentrations were noticeably reduced. These results indicate that GSH-dependent perturbation occurs as the result of the promotion of branched chain amino acid synthesis and an attenuation of cysteine and methionine synthesis, both of which activate the generation of $H_2S$. In a low sulfate medium containing 2.5 mM sulfate, the GSH injections did not result in perturbations of dissolved $O_2$ NAD(P)H redox oscillations without burst $H_2S$ production. This suggests that GSH-dependent perturbation is intimately linked with the metabolism of branched-chain amino acids and $H_2S$ generation, rather than with direct GSH-GSSG redox control.

• Proceedings of the Microbiological Society of Korea Conference
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• 2002.10a
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• pp.206-208
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• 2002

• Proceedings of the Korean Society of Life Science Conference
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• 2003.05a
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• pp.114-114
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• 2003