Kallikrein

Overview

Kallikrein measures a family of serine proteases, including plasma kallikrein (KLKB1 gene) and tissue kallikreins (KLK1-15 genes), that cleave kininogens to generate vasoactive kinins or activate other protease cascades. Plasma kallikrein contributes to the contact activation pathway of coagulation and bradykinin production, while prostate-specific kallikrein-3 (PSA) is a well-established tumor marker, and other tissue kallikreins participate in tissue remodeling. Elevated levels may indicate prostate cancer (PSA), inflammation, or hereditary angioedema activity, while deficiencies can cause coagulation disorders. Clinically, kallikrein measurement is most established for prostate-specific antigen (PSA) screening and monitoring, with other kallikreins primarily serving research roles in cancer and inflammatory biomarker discovery.

Clinical Use Cases

  • Prostate cancer screening, staging, and monitoring treatment response (PSA/kallikrein-3).
  • Evaluating hereditary angioedema and monitoring plasma kallikrein inhibitors.
  • Research assessment of kallikrein expression in ovarian, breast, and other hormone-related cancers.
  • Investigating inflammatory and tissue-remodeling processes in research settings.

Specimen Types

  • Serum (most common for PSA and circulating kallikreins).
  • Plasma (for plasma kallikrein activity assays).
  • Tissue biopsy (for tissue-specific kallikrein expression studies).

Measurement Methods

  • Immunoassay (ELISA or automated chemiluminescent for PSA).
  • Enzymatic activity assays for functional kallikrein measurement.
  • Mass spectrometry-based proteomics for research-grade kallikrein profiling.

Test Preparation and Influencing Factors

  • For PSA: avoid ejaculation, vigorous exercise, and prostate manipulation 48 hours prior.
  • Benign prostatic hyperplasia, prostatitis, and urinary tract infection elevate PSA.
  • Plasma kallikrein activity affected by C1-inhibitor levels and bradykinin pathway inhibitors.
  • Renal function and inflammation influence circulating tissue kallikrein levels.

Synonyms

  • Prostate-specific antigen (PSA) for KLK3.
  • Plasma prekallikrein (for circulating form).
  • Tissue kallikreins (KLK1-15 family).

Further Reading

  • “Prostate-Specific Antigen (PSA) Test” – MedlinePlus;