Saporin (SAP)

Saporin is a type I ribosome-inactivating protein (RIP) derived from the seeds of *Saponaria officinalis* (soapwort) and consists of a single catalytic polypeptide chain with N-glycosidase enzymatic activity[1][3][4]. This protein efficiently and irreversibly inactivates ribosomes by depurinating a universally conserved adenine in the 28S rRNA, thereby halting protein synthesis and inducing cell death[1][3]. Unlike type II RIPs (e.g., ricin), saporin lacks a lectin-like binding chain, which restricts its native cell entry but provides safety in handling and enables its use as a research tool and an immunotoxin payload[1][3]. Its remarkable stability—resistance to heat, proteases, and chemical modifications—makes it an attractive candidate for antibody-drug conjugate (ADC) and immunotoxin development aimed at selectively targeting cancer cells or other pathological tissue via specific ligands or antibodies[1][2][4]. Saporin-based immunotoxins have been studied in both hematological malignancies and solid tumors, as well as explored for viral infection treatments[1][2][4]. Notable safety concerns include vascular leak syndrome and immunogenicity, which have limited its clinical translation to date[1][4].

Other names

Saporin-SO6Sap-SO6SAPSaporin-6Ribosome-inactivating protein type 1 (RIP type I)Soapwort ribosome-inactivating protein

N-glycosidase activity: removes a specific adenine from 28S rRNA, irreversibly inactivating ribosomes and blocking protein synthesis, leading to cell death[1][3][4] When conjugated, immunotoxin delivers saporin specifically to target cells, which it kills by the above mechanism[1][2]