Albany 2015:Book of Abstracts
June 9-13 2015
©Adenine Press (2012)
Inhibition of Isocitrate Lyase Shifts Metabolism Toward the Isocitrate Overproduction in Yeast Yarrowia lipolytica
The commercial demand for DS-threo-isocitric acid has been grown because of its use as useful chiral building block for pharmaceutical products, anticoagulant in biological fluids, and a marker for detection of authenticity and quality of fruit products, in particular, citrus juices. According to our preliminary data, monopotassium salt of ICA could be applied in sport medicine as an antihypoxic agent that is based on revealing physiological role of ICA as a stimulator of energy processes during active functioning of the tricarboxylic acid cycle.
Isocitric acid is existing as four isomers: DS-erythro-isocitric acid, LS-erythro-isocitric acid, LS-threo-isocitric acid, and DS-threo-isocitric acid. Out of four isomers, only DS-threo-isocitric acid (ICA) is a natural compound presented in each living cell; this isomer is of practical interest, since the other three isomers are not metabolized in the cells, and even are inhibitors of several enzymes. In this connection, the sources of ICA acquire exceptional importance because only natural products can be used for the food and medical applications. Recently, we reported the microbiological ICA production with the use of yeast Yarrowia lipolytica (Kamzolova et al. 2013). However, the production of ICA by yeast meets serious difficulties, since it is accompanied by a simultaneous production of citric acid (CA) in significant amounts that reduces the yield of desired product (Morgunov, Kamzolova 2013).
In the present study, the biosynthesis of ICA by Y. lipolytica VKM Y-2373 from rapeseed oil and its regulation by oxalic- and itaconic acids - inhibitors of isocitrate lyase (ICL) - a key enzyme the ICA metabolism were studied. It was shown that oxalic- and itaconic acids in a concentration of 2 and 1 mM, respectively, cause practically complete inhibition of ICL reaction in intracellular homogenate of Y. lipolytica. In the presence of 30-50 mM oxalic acid Y. lipolytica produces isocitrate and citrate in a ratio of 2:1, while the production of ICA and CA was similar without an oxalic acid. A similar effect, but more pronounced, took place in the presence of itaconic acid. It was shown that inhibition of ICL by 30-40 mM itaconic acid leads to presumable synthesis of isocitrate in a ratio of 6:1. In a fermentor in the presence of itaconic acid yeast Y. lipolytica VKM Y-2373 produced 88.7 g/l ICA and 15.1 g/l CA with yield of 90%. The developed method for ICA production can compete with the existing costly method of ICA production from the juice of specially-cultivated plants Sedum spectabile.
The reported study was partially supported by Russian Foundation of Basic Research (RFBR) and Government of Moscow oblast, research project No. 14-48-03540 "r_center_".
I.G. Morgunov, S.V. Kamzolova (2013) The peculiarities of regulation of Yarrowia lipolytica yeast and citric acid overproduction. J Biomol Struct Dyn 31 (sup1), 122-123.
Svetlana V. Kamzolova
G.K. Skryabin Institute of Biochemistry and Physiology of Microorganisms RAS