engleski

Influence of Growth Conditions on Sphingoid Bases Biosynthesis in Yeast

Sphingolipids are defined as compounds that have a common long-chain sphingoid base. They usually occur in yeasts as inositolphosphoceramides. The majority of these compounds are sizuated in the plasma membrane. They are indispensable for the growth and viability of the cells. Sphingolipids are thought to play important rolesin various yeast activities, including the modulation of the plasma membrane H+-ATP-ase, the membrane signaling pathwaya, the regulation of phospholipid biosynthesis, cell wall biosynthesis and anchoring of the cell surface glycoproteins. Besides, there is some evidence they are engaged in signal transduction pathways, since their breakdown products (that is long-chain sphingoid bases) are bioactive molecules. Sphingolipids backbones (phytosphingosine and phytoceramide) are proved to be essential for viability when cells are grown under conditions of extreme pH ot temperature. Yeast can be utilised as a potential source of sphingoid base since sphingolipids in yeasts represent approximately 40% of total inositol-containing lipids. Yeasts are very suitable for the production of long-chain sphingoid bases as they grow fast and modifying growth conditions can markedly change the quantity and content of their lipids. Four distinct yeasts were used in our experiments with the aim of the sphingoid bases overproduction: Rhodotorula glutinis, Saccharomyces uvarum, Hansenula anomala and Candida lipolytica 33. Cells were grown in synthetic medium containing glucose (1%) as the sole carbon source. Experiments were carried out on shaker at 28oC. The production of sphingoid bases was affected ba addition of the compounds, which are involved in sphingoid bases biosynthesis or activate key enzymes in that pathway. Cell turbidity was monitored by measurement of absorbance at 650 nm. The quantity of total sphingoid bases was determined spectrophotometrically at 415 nm. The structure and quantity of a particular sphingoid base in yeast samples was established by HPLC. The obtained results point to the following conclusions: yeasts accumulate different quantities of sphingolipids depending upon growth conditions; the mayor distinction between analysed yeasts is that they contain diverse sorts and amounts of sphingoid bases.

Sphingolipids; Sphingoid bases; Yeast

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