invertases

Invertases are enzymes that catalyze the hydrolysis of sucrose into glucose and fructose. They are members of the glycoside hydrolase family 32 and occur in a broad range of organisms, including plants, yeasts, and bacteria. In plants and microbes, invertases support sugar utilization, carbon partitioning, and osmotic adjustment, contributing to growth and development.

Plant invertases are typically categorized as acid invertases and neutral/alkaline invertases. Acid invertases have optimum pH around 4.5–5.5 and include cell wall invertases, which are secreted into the apoplast, and vacuolar invertases, which reside in vacuoles. Neutral/alkaline invertases function mainly in the cytosol or other organelles and operate at higher pH. Invertases are often glycoproteins, with plant enzymes commonly bearing N-linked glycans; neutral invertases usually lack signal peptides and are cytosolic.

Reaction and mechanism: invertases hydrolyze the 1,2-glycosidic bond of sucrose, yielding equimolar glucose and fructose. The reaction typically proceeds via an inverting mechanism that changes the anomeric configuration of the substrate, producing invert sugar. Structure and localization vary: acid invertases are secreted or vacuolar, while neutral invertases are intracellular.

Physiological roles: in plants, invertase activity influences sink strength, phloem unloading, seed germination, pollen tube growth, and responses to abiotic or biotic stress. In microorganisms, invertases enable growth on sucrose as a carbon source. Regulation occurs at transcriptional, post-translational, and sugar-signaling levels, integrating developmental cues and sugar status.

Industrial and research uses: invertases are employed to produce inverted sugar syrups for baking and confectionery, where glucose and fructose provide different sweetness and fermentation properties. They are used in fermentation processes and as tools for studying plant and microbial sugar metabolism.