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4 Overview of Fungal Biosynthetic Pathways Anabolic pathways are energy-consuming, reductive processes which lead to the biosynthesis of new cellular material and are mediated by dehydrogenase enzymes which predominantly use reduced NADP+ as the redox cofactor. 1). In S. cerevisiae, up to P1: OTA/XYZ JWST082-01 P2: ABC JWST082-Kavanagh 20 June 15, 2011 19:28 Printer Name: Yet to Come INTRODUCTION TO FUNGAL PHYSIOLOGY 20 % of total glucose may be degraded via the hexose monophosphate pathway. This pathway generates cytosolic NADPH (following the dehydrogenation of glucose 6-phosphate using glucose 6-phosphate dehydrogenase and NADP+ as hydrogen acceptor) for biosynthetic reactions leading to the production of fatty acids, amino acids, sugar alcohols, structural and storage polysaccharides and secondary metabolites.

Numerous physical, chemical and biological factors influence fungal cell death, which may be defined as complete and irreversible failure of cells to reproduce. Fungi will die if confronted with excessive heat, extreme cold, high-voltage electricity, ionizing radiation, high hydrostatic and osmotic pressures and if exposed to chemical or biological fungicidal agents. When the cells’ physiological protection responses are insufficient to counteract the cellular damage caused by physical stress, cells will die.

G. 45 ◦ C), salt (to encourage plasmolysis) and solvents (to promote lipid dissolution). Exogenous hydrolytic enzymes, such as papain, can also be used to accelerate cell-wall breakdown. Genetic factors also influence fungal cell death. For example, cells may commit suicide following DNA damage, presumably to avoid the risk of producing genetically altered progeny. Cellular ageing and apoptotic cell death have been widely studied in yeasts, especially in S. cerevisiae, which is a valuable model organism for understanding molecular genetic basis of the ageing process in eukaryotic cells.