ubiquitinaser

Ubiquitinase is not a standard term in modern biochemistry. In many contexts it is used loosely to refer to enzymes involved in ubiquitin processing, either ubiquitin ligases that attach ubiquitin to substrates or deubiquitinases that remove ubiquitin. The more precise terms are E3 ubiquitin ligases and deubiquitinases (DUBs). Because the word is not consistently defined, its exact meaning can vary by source, and it is often considered a nonstandard synonym for ubiquitin-related enzymes.

Ubiquitination is a post-translational modification in which ubiquitin, a small 76-amino-acid protein, is covalently linked to substrate proteins. The canonical cascade involves an E1 activating enzyme, an E2 conjugating enzyme, and an E3 ligase that transfers ubiquitin to lysine residues on the substrate, forming mono- or polyubiquitin chains. The fate of the substrate frequently depends on the type of ubiquitin linkage; for example, K48-linked chains commonly signal for degradation by the 26S proteasome, while other linkages regulate trafficking, signaling, or DNA repair. Removal of ubiquitin is performed by deubiquitinases, which cleave isopeptide bonds and can recycle ubiquitin or rescue substrates from degradation.

Classification and examples are as follows. E3 ubiquitin ligases are grouped into RING, HECT, and RBR families, each with distinct catalytic mechanisms for transferring ubiquitin. Deubiquitinases constitute several families, including ubiquitin-specific proteases (USPs), UCHs, OTUs, and JAMMs, among others. Both E3 ligases and DUBs are highly specific for substrates and ubiquitin linkage types, enabling precise regulation of cellular pathways.

Dysregulation of ubiquitin-processing enzymes is linked to diseases such as cancer and neurodegeneration. Therapeutic strategies include proteasome inhibitors and, more recently, modulators of specific E3 ligases or DUBs, aiming to alter protein stability and signaling.