Calcium induced alterations in structural and functional role of phospholipids in Microsporum gypseum.

The effect of calcium on the structural and functional aspects of phospholipids in Microsporum gypseum was examined. Cells grown in presence of calcium exhibited increased content of phospholipids and enhanced synthesis of phospholipids as monitored by the incorporation of [32P] orthophosphoric acid. The rise in the levels of phospholipids was found to be due to increased synthesis of fatty acids as observed from [14C] acetate incorporation studies. The rise in the levels of phospholipids were reflected in the subcellular fractions also. Change in the phospholipid composition increased the fluidity of the membrane as is evident from fluorescence polarization studies using 1-anilinonaphthalene-8-sulfonate (ANS) and 1,6-diphenyl-1,3,5-hexatriene (DPH). The increased membrane fluidity was consistent with the enhanced uptake of [3H] proline in calcium grown cells.

Influence of cyclic AMP on the biosynthesis of phosphatidylcholine in Microsporum gypseum.

The influence of intracellular cAMP on phosphatidylcholine biosynthesis in Microsporum gypseum has been examined using radiolabelled precursors. The incorporation of labelled choline, methionine and ethanolamine into total lipids, phospholipids and choline containing phospholipids increased in aminophylline and decreased in atropine grown cells as a result of rise and fall in cAMP levels in these cells. The enhanced uptake of labelled methionine and ethanolamine in comparison to labelled choline in choline containing phospholipids in aminophylline grown cells suggests that methylation pathway is more influenced by cAMP than CDP-choline pathway.

Further studies on the influence of aminophylline on lipids of Microsporum gypseum.

Aminophylline added to the growth medium of Microsporum gypseum for varying periods exhibited varied effects on lipid synthesis. A decreased incorporation of [14C]acetate into both lipids and phospholipids was initially observed which showed increase after 24 hr of incubation. Short-time exposure of aminophylline also resulted in decreased activity of glycerol-3-phosphate acyltransferase, the key enzyme of lipid synthesis, which, however, got stimulated on longer incubation, supporting the decreased/increased synthesis of lipids during short/long time exposure. Changes in the intracellular levels of cAMP at different time points account for the induced alterations in lipid synthesis, possibly due to formation of metabolites of aminophylline during growth of the organism.