Isolation from Human Seminal Plasma of an Abundant 16‐kDa Protein Originating from the Prostate, Its Identification with a 94‐Residue Peptide Originally Described As β‐Inhibin

In addition to other known markers of the human prostate, it was shown that the prostatic fraction of the split ejaculate was rich in a 16-kDa protein with properties not described previously. This protein was purified from human seminal plasma using ammonium sulfate precipitation, DEAE-Sepharose CL-6B ion exchange chromatography, and gel filtration on Sephadex G-100. The purified protein showed a single prominent spot on two-dimensional gel electrophoresis. The sequence of the first 40 amino acids that could be positively identified was identical to that of a prostatic secretory protein of 94 amino acids (PSP94) previously designated as beta-inhibin. Antibodies produced in rabbits against the purified protein were used to develop a radioimmunoassay. These antibodies appeared to recognize only the NH2-terminal portion of the native molecule since they did not react with a synthetic peptide composed of the 28 C-terminal residues. The radioimmunoassay showed that the concentration of the protein was 1320 +/- 183 micrograms/ml in the seminal plasma of adult fertile men and 1134 +/- 136 micrograms/ml in vasectomized patients. In hypertrophic and adenocarcinomatous prostates, the concentrations were 326 +/- 156 and 104 +/- 23 micrograms/ml, respectively, while values were lower than 0.060 micrograms/ml in the testis, epididymis, vas deferens and liver. The blood plasma concentration was 0.019 +/- microgram/ml in 23 asymptomatic men 45 to 65 years old and 0.115 +/- 0.036 microgram/ml in eight patients with prostate cancer.(ABSTRACT TRUNCATED AT 250 WORDS)