The Mycota : A Treatise on the Biology of Fungi with Emphasis on Systems for Fundamental and Applied Research Vol III edition:Third Edition pages:191-277
Trehalose is a nonreducing disaccharide (α,α-1,1-diglucose) commonly found in many fungi and present in particularly high concentrations in quiescent cells and survival forms. For a long time trehalose was only considered as a storage carbohydrate, but later work has revealed multiple roles, in particular as a stress protectant. The dominant pathway for trehalose biosynthesis in fungi is through trehalose-6-phosphate synthase and phosphatase, while two major types of trehalases are responsible for its breakdown. Trehalose levels vary strongly with the growth phase of the cells, with rapidly growing cells having lower levels than slow-growing and stationary-phase cells. The regulatory pathways involved in control of nutrient-induced trehalose mobilization have been studied in great detail in the yeast Saccharomyces cerevisiae. Activation of trehalase and mobilization of trehalose are very convenient readouts for elucidation of nutrient-sensing and signaling pathways. Glucose-induced mobilization is triggered by GPCR and glycolytic signaling, resulting in cAMP-dependent activation of protein kinase A, while activation by other nutrients is mediated by plasma membrane transceptors (transporter-receptors) that trigger activation of PKA in an unknown way, without using cAMP as a second messenger. The intermediate of trehalose biosynthesis, trehalose-6-phosphate, has emerged as an important regulator of glycolysis. Because of its importance for stress tolerance, trehalose metabolism has also been explored as a possible target for antifungals.