Chapter 3.3.3 - Biosynthetic Enzymes for (1-3)-β-Glucans, (1-3;1-6)-β-Glucans from Yeasts: Biochemical Properties and Molecular Biology

Abstract

This chapter reviews the biosynthesis of β-glucans: the polymerizing enzymes and regulatory components required for β-glucan synthesis and their regulation. β-Glucans, major polymers of the yeast cell wall structure, have important roles in the function of the cell wall. Synthesis of the cell wall is tightly regulated through a process that is intimately associated with cell growth and morphogenesis. Cell wall precursors are polymerized at the cell surface and then modified and connected to each other. (1,3)-β-glucan is the main β-glucan synthesized by a (1,3)-β-glucan synthase complex, consisting of a catalytic subunit encoded by the FKS1 and FKS2 genes, and a regulatory subunit encoded by the RHO1 gene. (1,3)-β-Glucan synthesis is spatio-temporally modulated by directly controlling enzyme activity or indirectly regulating expressions. These regulatory mechanisms enable organisms to respond to exogenous and endogenous stimuli to protect against environmental changes.