Plasmiinin

Plasmiinin is a hypothetical secreted protein proposed to regulate plasmin, the central serine protease of the fibrinolytic system. In the speculative model, plasmiinin binds to plasmin with micromolar to nanomolar affinity, inhibiting its activity and limiting fibrin degradation during inflammation or wound healing. The concept of plasmiinin has appeared in theoretical discussions of plasmin regulation but has not been established as a confirmed molecular entity.

Proposed characteristics include a signal peptide for secretion, a single polypeptide chain of around 25–35 kDa, and post-translational glycosylation. Predicted to adopt a compact fold with surface-exposed regions that present plasmin-binding motifs. No experimental structure or definitive sequence data have been published in peer-reviewed primary literature.

Function and mechanism: By sequestering active plasmin, plasmiinin would slow fibrinolysis, potentially stabilizing clots in healing tissue or during inflammatory responses. It may interact with other regulators, such as alpha-2-antiplasmin or plasminogen activator inhibitors, to fine-tune proteolysis.

Physiological context: If real, plasmiinin would presumably be expressed in liver-derived plasma or locally in inflammatory sites. Its expression could be modulated by cytokines or coagulation signals, linking coagulation and immune responses.

Status and naming: The name plasmiinin is derived from plasmin and the common protein suffix -in. As of current reviews, plasmiinin remains hypothetical, with no confirmed gene, isoform, or experimental validation.