Human glandular kallikrein, hK2, shows arginine-restricted specificity and forms complexes with plasma protease inhibitors

✍ Scribed by Mikolajczyk, Stephen D.; Millar, Lisa S.; Kumar, Abhay; Saedi, Mohammad S.

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 204 KB
• Volume: 34
• Category: Article
• ISSN: 0270-4137
• DOI: 10.1002/(sici)1097-0045(19980101)34:1<44::aid-pros6>3.0.co;2-k

✦ Synopsis

BACKGROUND. Human glandular kallikrein (hK2) is a new potential marker for prostate cancer. It is a serine protease expressed in human prostate epithelial cells which has 78% sequence identity with prostate-specific antigen (PSA). PSA is a widely used biochemical marker for prostate cancer. METHODS. Recombinant hK2 expressed in mammalian cells was purified to homogeneity by immunoaffinity chromatography, using an anti-hK2 mAb. hK2 enzymatic specificity was determined on peptide substrates by N-terminal amino acid sequencing. hK2 complexes were analyzed by SDS-PAGE and Western blots. RESULTS. hK2 was found to cleave peptide substrates exclusively at selected arginine residues. An amidolytic activity of 4,100 pmol/min per g hK2 was obtained on the chromogenic substrate H-D-Pro-Phe-Arg-p-nitroanilide, while no activity was found on methoxysuccinyl-Arg-Pro-Tyr-p-nitroanilide, a chymotrypsin substrate used to measure PSA activity. hK2 complexed completely with ␣ 1 -antichymotrypsin and ␣ 2 -antiplasmin after 4 hr at 37°C, but showed no detectable complex with antithrombin III and ␣ 1 -protease inhibitor under these conditions. hK2 also formed a rapid complex with ␣ 2 -macroglobulin. CONCLUSIONS. These results demonstrate that hK2 is an active protease with arginineselective specificity, which forms covalent complexes with plasma protease inhibitors.