Ho-Yong Sohn

Ultradian oscillation of Saccharomyces cerevisiae during aerobic continuous culture: hydrogen sulphide mediates population synchrony

Saccharomyces cerevisiae showed an ultradian respiratory oscillation during aerobic continuous culture. Analysis of the off‐gas revealed that hydrogen sulphide production also oscillated. Production was first detected at the onset of low respiration and reached a maximum (1.5 µM) prior to minimum respiratory activity. Then H2S concentration fell rapidly to below 0.2 µM before the onset of high respiration. Injection of respiratory oscillation perturbation agents, such as glutathione (50 µM), NaNO2 (50 µM) or acetaldehyde (4.5 mM), transiently increased H2S production above 6 µM. The synchronization properties of H2S were analysed to reveal that changes of oscillation period and amplitude were dependent on H2S concentration in culture. It is concluded that H2S produced during oscillation produces population synchrony by respiratory chain inhibition. Copyright

Involvement of oxidative stress in the regulation of H2S production during ultradian metabolic oscillation of Saccharomyces cerevisiae

Periodic evolution of H(2)S during aerobic chemostat culture of Saccharomyces cerevisiae resulted in ultradian metabolic oscillation via periodic inhibition of respiratory activity. To understand the nature of periodic H(2)S evolution, we investigated whether oxidative stress is associated with H(2)S production. The cellular oxidative states represented by intracellular level of lipid peroxides oscillated out of phase with the oscillation of dissolved O(2). Pulse addition of antioxidant, oxidative agent or inhibitor of antioxidation enzymes perturbed metabolic oscillation producing changes in H(2)S evolution. Analysis of H(2)S production profiles during perturbation of oscillation revealed that the amount of H(2)S production is closely linked with cellular oxidative states. Based on these results and our previous reports, we suggest that oxidative stresses result in periodic depletion of glutathione and cysteine, which in turn causes stimulation of the sulfate assimilation pathway and H(2)S production.

Mathematical analysis of a mechanism for autonomous metabolic oscillations in continuous culture of Saccharomyces cerevisiae

Autonomous metabolic oscillations were observed in aerobic continuous culture of Saccharomyces cerevisiae. Experimental investigation of the underlying mechanism revealed that several pathways and regulatory couplings are involved. Here a hypothetical mechanism including the sulfate assimilation pathway, ethanol degradation and respiration is transformed into a mathematical model. Simulations confirm the ability of the model to produce limit cycle oscillations which reproduce most of the characteristic features of the system.

Antifungal Activity of Phenanthrene Derivatives from Aerial Bulbils of Dioscorea batatas Decne

Plants of the genus Dioscorea have long been used as oriental folk medicine, and Dioscorea batatas Decne has been cultivated for healthy food in Korea. Although the bulbils were produced 2,000 ton annually, there are few reports for bioactive compounds in bulbils. In this study, three phenanthrenes and two phenanthraquinones were isolated from the aerial bulbils of D. batatas Decne, and their structures were elucidated. Among them, compound 2 (6-hydroxy-2,7-dimethoxy-1,4-phenanthraquinone) has not been reported previously. Evaluation of antimicrobial activities based on disk-diffusion assay, MIC and MFC showed the compound 12 (6,7-dihydroxy-2,4-dimethoxyphenanthrene) has strong antimicrobial activity with 25 ㎍/㎖ of MIC and MFC against Candida albicans. Our results suggested that compound 12 has a potent antifungal activity, and the antimicrobial activity and its spectrum are modulated by hydroxylation and methoxylation of phenanthrene ring moiety of the compound.

Adaptive stress response to menadione-induced oxidative stress in Saccharomyces cerevisiae KNU5377

The molecular mechanisms involved in the ability of yeast cells to adapt and respond to oxidative stress are of great interest to the pharmaceutical, medical, food, and fermentation industries. In this study, we investigated the time-dependent, cellular redox homeostasis ability to adapt to menadione-induced oxidative stress, using biochemical and proteomic approaches in Saccharomyces cerevisiae KNU5377. Time-dependent cell viability was inversely proportional to endogenous amounts of ROS measured by a fluorescence assay with 2′,7′-dichlorofluorescin diacetate (DCFHDA), and was hypersensitive when cells were exposed to the compound for 60 min. Morphological changes, protein oxidation and lipid peroxidation were also observed. To overcome the unfavorable conditions due to the presence of menadione, yeast cells activated a variety of cell rescue proteins including antioxidant enzymes, molecular chaperones, energy-generating metabolic enzymes, and antioxidant molecules such as trehalose. Thus, these results show that menadione causes ROS generation and high accumulation of cellular ROS levels, which affects cell viability and cell morphology and there is a correlation between resistance to menadione and the high induction of cell rescue proteins after cells enter into this physiological state, which provides a clue about the complex and dynamic stress response in yeast cells.

Evaluation of Antioxidant and Nitrite Scavenging Activity of Seaweed Extracts

유용생리활성의 해조류를 이용한 식품소재 개발 연구의 일환으로, 35종 해조류(갈조류 17종, 홍조류 11종 및 녹조류 7종)의 메탄올 추출물을 대상으로 in-vitro 항산화 및 nitrite 소거활성을 평가하였다. 해조류 추출물(

Evaluation of In-vitro Anticoagulation Activity of 35 Different Seaweed Extracts

500\;{\mu}g/ml

Evaluation of In-vitro Anticoagulation Activity of 33 Different Medicinal Herbs

) 중 감태, 곰피, 대황, 넓패, 패, 모자반, 알송이모자반, 야마자모자반 및 잘피의 9종에서 60% 이상의 DSA 활성을 나타내었으며, ASA활성은 DSA활성과 높은 상관관계를 나타내었다(상관계수 0.855). 환원력 평가 결과에서는 감태, 곰피 및 대황의 3종만이 0.88 (

GLR1 Plays an Essential Role in the Homeodynamics of Glutathione and the Regulation of H2S Production during Respiratory Oscillation of Saccharomyces cerevisiae

Abs_{700}

Anti-proliferative Activities of Solvent Fractions of Lees Extracts in Human Colorectal HCT116 Cells

) 이상의 강력한 활성을 나타내었다. 한편 식품에서의 발암인자인 nitrosoamine생성억제와 관련된 NSA평가의 경우, 전체 35종의 해조류 중 19종에서 60% 이상의 NSA를 나타내었으며, 특히 기존에 알려지지 않은 모자반, 야마다모자반, 알송이모자반, 패, 넓패에서 우수한 활성을 확인하였다. 1차 선별된 9종 해조류의 DSA, ASA, NSA의