levansucraseactive

Levansucrase active, often discussed in connection with levansucrase enzymes, is a nonstandard term used to denote the catalytically competent form of levansucrase. Levansucrases are enzymes that catalyze the transfer of fructosyl units from sucrose to form levan, a fructan polymer, and they can also hydrolyze sucrose to glucose and fructose. The designation “active” may appear in databases or literature to distinguish a functional enzyme from an inactive mutant, truncated form, or denatured preparation.

Levansucrases belong to glycoside hydrolase family 68 and are produced by various bacteria, including Bacillus species. The typical reaction involves sucrose as donor and an acceptor (often the growing levan chain) to produce high-molecular-weight levan with predominantly β-(2→6) linkages, along with minor transfructosylation products and, when branch formation occurs, some β-(2→1) linkages. The enzymes can also perform hydrolysis of sucrose when acceptor availability is limited.

In terms of mechanism, levansucrases operate via a retaining glycosyltransferase process that forms a covalent fructosyl-enzyme intermediate before transferring the fructosyl moiety to an acceptor. The active site contains residues that function as the catalytic nucleophile and acid/base, coordinating substrate binding and transfer. Structural features typically include a catalytic core with substrate-binding pockets and, in some variants, auxiliary domains that influence substrate specificity and polymer size.

Biotechnological use centers on enzymatic production of levan and related fructans, which have applications as prebiotics, texturizers, and stabilizers in food and pharmaceuticals. In some bacteria, the sacB gene encodes levansucrase and is used as a negative selection marker in genetic systems, illustrating the enzyme’s physiological and biotechnological relevance.