Semenogelin I and II
Definition
High-molecular-weight proteins secreted by the seminal vesicles that form the semen coagulum immediately after ejaculation. PSA then cleaves them to liquefy the ejaculate. Both are highly semen-specific and are the target of RSID-Semen.
- Source
- Seminal vesicle secretions
- Role
- Form the semen coagulum after ejaculation
- Cleaved by
- PSA (prostate-specific antigen)
- Specificity
- Highly semen-specific
- Detection method
- Target antigen of RSID-Semen lateral-flow test
Common questions
Why does PSA cleave semenogelin after ejaculation?+
PSA is a protease that liquefies the initial gel-like coagulum formed by semenogelin, allowing sperm to become motile within roughly 20 to 30 minutes. This liquefaction process is a normal physiological step, not a degradation of forensic evidence.
How does targeting semenogelin improve on older presumptive semen tests?+
Older tests like the acid phosphatase test detect an enzyme activity that occurs at lower levels in some other body fluids and degrades faster in the stain. Semenogelin-based immunoassays like RSID-Semen are confirmatory and highly specific, reducing false positives from non-seminal sources.
Can semenogelin still be detected in samples from vasectomised men?+
Yes, because semenogelin is produced by the seminal vesicles rather than the testes, it remains present in the ejaculate of azoospermic or vasectomised individuals, unlike sperm-cell-based identification methods.
Related terms
- ABAcard P30 (HemaTrace P30)
- A lateral-flow immunochromatographic card that detects PSA at approximately 0.2-4 ng/mL of extract. Widely used in sexual assault kit triage because it...
- Prostate-Specific Antigen (PSA / P30)
- A glycoprotein produced by the prostate gland and secreted into seminal plasma at high concentrations. The PSA immunochromatographic strip test is the...
- RSID-Semen
- Rapid Stain Identification of Semen: an immunochromatographic lateral-flow strip from Independent Forensics that detects semenogelin I and II with sensitivity to approximately...
- Sensitivity and Specificity in Forensic Context
- Sensitivity is the probability of a positive result when semen is truly present; specificity is the probability of a negative result when...
- Seratec PSA Semiquant
- A lateral-flow PSA strip with a semi-quantitative band-intensity scale. Line intensity corresponds approximately to 1 ng/mL, 2 ng/mL, or greater concentrations, useful...