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Albany 2019: 20th Conversation - Abstracts

category image Albany 2019
Conversation 20
June 11-15 2019
Adenine Press (2019)

Deficiency of Thiamine Shifts Metabolism Toward the α-Keto Acids Oversynthesis in Yarrowia lipolytica Yeast

Earlier, we found that the inhibition of isocitrate lyase by oxalic and itaconic acids shifts yeast metabolism toward the threo-Ds-isocitric acid synthesis, a biologically active compound, an intermediate of Krebs cycle (Kamzolova, Morgunov 2015; Kamzolova et al. 2016a).

The purpose of this work was to study the effect of limited growth of Yarrowia lipolytica yeast by a thiamine, which is essential for multiple biochemical pathways involved in glucose catabolism.

It was shown that the growth curve of Y. lipolytica VKM Y-2378 had three phases: exponential phase (up to 12 h), retardation phase (from 12 to 24 h) caused by exhaustion of thiamine, and stationary phase. The production of α-keto acids (pyruvate and α-ketoglutarate) began in the growth retardation phase and continued in the stationary phase. At the end of cultivation, cells synthesized 41 g/L pyruvate and 8 g/L α-ketoglutarate. The thiamine deficiency disturbed the metabolic flow through the thiamine-dependent enzymes of glucose catabolism. The inhibition of pyruvate dehydrogenase complex leads to excretion of pyruvate from the yeast cells. As the inhibition of pyruvate dehydrogenase is not complete, the formation of acetyl-CoA continues, providing for the synthesis of α-ketoglutarate in Krebs cycle. α-Ketoglutarate is not oxidized in Krebs cycle since thiamine deficiency limits α-ketoglutarate dehydrogenase, and hence it is excreted from the yeast cells. The deficiency of energy at the level of thiamine-dependent enzymes affected the respiratory chain of cells. To maintain the with induced α-keto acids production, the cells activated the initial reactions of glucose catabolism and Krebs cycle. It is confirmed by increased activities of hexokinase, glucose-6-phosphate dehydrogenase, fructose bisphosphate aldolase, pyruvate kinase, citrate synthase and aconitate hydratase; oxaloacetate in this case is presumably resynthesized by means of pyruvate carboxylase reaction.

Similar effect of a thiamine deficiency has been previously demonstrated for Blastobotrys adeninivorans grown on glucose (Kamzolova, Morgunov 2016b) and Y. lipolytica VKM Y-2378 grown on glycerol-containing waste of biodiesel production (Kamzolova, Morgunov 2018), an active superproducers of α-keto acids. Therefore, it can be suggested that this phenomenon is a common regularity associated with the limitation of the activity (or synthesis) of enzymes involved in carbohydrate utilization and α-keto acids production.

References
    Kamzolova, S.V., Morgunov, I.G. (2015) Inhibition of isocitrate lyase shifts metabolism toward the isocitrate overproduction in yeast Yarrowia lipolytica. J. Biomol. Struct. Dyn. 33, Suppl. 1, 107-108. doi: 10.1080/07391102.2015.1032802

    Kamzolova, S.V., Allayarov, R.K., Lunina, J.N., Morgunov, I.G. (2016a) The effect of oxalic and itaconic acids on threo-Ds-isocitric acid production from rapeseed oil by Yarrowia lipolytica. Bioresour. Technol. 206, 128-133. doi: 10.1016/j.biortech.2016.01.092.

    Kamzolova, S.V., Morgunov, I.G. (2016b) Biosynthesis of pyruvic acid from glucose by Blastobotrys adeninivorans. Appl. Microbiol. Biotechnol. 100(17), 7689-7697. doi: 10.1007/s00253-016-7618-1.

    Kamzolova, S.V., Morgunov, I.G. (2018) Biosynthesis of pyruvic acid from glycerol-containing substrates and its regulation in the yeast Yarrowia lipolytica. Bioresour. Technol. 266, 125-133. doi: 10.1016/j.biortech.2018.06.071.

Igor G. Morgunov
Svetlana V. Kamzolova

G.K. Skryabin Institute of Biochemistry and Physiology of Microorganisms
RAS Pushchino
Moscow region 142290, Russia

Ph: (007) 9165251329
Fx: (007) 495-9563370
Email: morgunovs@rambler.ru