Nonbiotin

Nonbiotin is a term employed in biochemical and molecular biology to denote molecules, proteins, or biological systems that lack covalently attached biotin or that do not participate in biotin-dependent reactions. Biotin is a water‑soluble vitamin that serves as a cofactor for carboxylases and ligases involved in important metabolic pathways. When biotin is absent or removed, the resulting nonbiotin form can be used experimentally to probe the functional role of biotinylation, to generate biosensors, or to create protein variants that are resistant to biotin‑based purification methods.

In laboratory practice, nonbiotin variants are often produced through genetic mutagenesis that eliminates lysine residues normally harboring the biotin moiety, or by chemical de‑biotinylation. Those proteins that naturally lack biotin-binding sites are referred to as nonbiotin proteins; examples include many structural cytoskeletal proteins and DNA‑binding proteins. Conversely, engineered nonbiotin tags are introduced into proteins that would otherwise be biotinylated to avoid background binding in streptavidin‑based assays.

The study of nonbiotin forms provides insight into the mechanistic importance of biotinylation. It also facilitates the development of novel therapeutic strategies, such as designing inhibitors that target biotin-dependent enzymes without affecting nonbiotin enzymes. In the broader context of nutrition, nonbiotin deficiency is assessed through the lack of biotin in plasma or tissues, contributing to the diagnosis of biotin deficiency disorders.