betafructofuranosidases

Beta-fructofuranosidases, commonly called invertases, are glycoside hydrolases that catalyze the hydrolysis of beta-D-fructofuranosides to release monosaccharides. The most familiar substrate is sucrose, which is cleaved into glucose and fructose to yield invert sugar. Invertases are assigned to glycoside hydrolase family 32 (GH32) and include enzymes that act on sucrose as well as those that hydrolyze fructans such as inulins and levans. They occur as extracellular enzymes secreted by microbes and plants, as well as intracellular forms in fungi and yeasts, and in some plants as membrane-associated variants.

Biological roles and distribution: In yeasts such as Saccharomyces cerevisiae, invertase is encoded by SUC2 and enables growth on sucrose by hydrolyzing extracellular sucrose. Plant invertases regulate carbon partitioning between source and sink tissues, while fungal and bacterial invertases contribute to nutrient acquisition in diverse environments. Some enzymes function on fructans via endo- and exo-acting activities, broadening substrate ranges beyond simple sucrose.

Mechanism and structure: GH32 enzymes share a five-bladed beta-propeller fold and employ a catalytic Asp–Glu dyad. Conserved motifs, including NDPNG, participate in substrate binding and catalysis. The active site accommodates sucrose and fructan substrates, enabling cleavage of the glycosidic bond and release of fructose and glucose.

Industrial relevance and properties: Invertases are used to produce inverted sugar syrups for confectionery and baking, improving sweetness and fermentability. Enzymes are sourced from yeast, fungi, and bacteria, with process conditions varying by source; secreted forms typically exhibit optima around pH 4.5–5.5 and temperatures from ~30 to 60°C.

Regulation: In yeast, SUC2 expression is inducible by sucrose and repressed by high glucose via catabolite repression. Secreted invertases often carry signal peptides for extracellular localization.