Prostate Specific Antigen (non-complexing fPSA)

General Product Information

Free PSA (fPSA) is isolated from human seminal fluid and is supplied as a liquid in 10mM Tris, 0.1% Sodium Azide, pH 8.0 ± 0.1. The non-complexing form is purified from material used to prepare the PSA-ACT Complex. The protein concentration for P0723 is determined by immunoassay. The protein concentration for other forms is determined by A280 using an extinction coefficient of 1.86 (Emg/ml = 1.86). Both of the complexed forms are prepared by in-vitro complex formation with the purified proteins. PSA-ACT complex is supplied as a liquid in 10mM Sodium Acetate, 150mM Sodium Chloride, 0.1% Sodium Azide, pH 5.6 ± 0.1. The protein concentration is determined by A280 using an extinction coefficient of 1.0 (Emg/ml = 1.0). PSA-A2M is supplied as a liquid in 20mM Sodium Phosphate, 150mM Sodium Chloride, 0.05% Sodium Azide, pH 7.4 ± 0.1. Protein is determined using the Bradford method (BSA standard).

Prostate Specific Antigen (PSA), a glycoprotein of the glandular kallikrein family, is a serine protease with chymotrypsin-like enzymatic activity. It has a molecular weight of approximately 33,000-34,000 Da and is found primarily in prostate tissue and seminal fluid. Serum levels of PSA are very low in healthy individuals (0 - 4 ng/ml), but are often elevated in malignant and benign prostatic disease. As such, immunoassays for serum levels of PSA have proven useful in the diagnosis and follow-up of prostate cancer.

PSA released into circulation is present as unbound, free PSA (fPSA) or bound to serum protease inhibitors, such as α1-antichymotrypsin (ACT) and α2-macroglobulin (A2M). Research indicates that immunoassays for serum levels of PSA alone cannot be relied on to distinguish prostate cancer from benign prostatic hyperplasia (BPH). Serum levels of PSA-ACT complex are reportedly higher in patients with prostate cancer than in those with BPH. As such, measuring the ratio of PSA-ACT to fPSA in patient samples is proving valuable in the differential diagnosis os prostate cancer. In addition, immunoassays for PSA-A2M serum levels may prove valuable in prostate cancer diagnosis, but further study is required.

See Also

• Monoclonal and Polyclonal Antibodies for PSA.