A 70-year-old man with known prostate carcinoma has a markedly elevated serum acid phosphatase with a disproportionate rise in prostatic fraction. Which isoenzyme is specifically measured to confirm prostatic origin?
- A Tartrate-resistant acid phosphatase (TRAP)
- B Prostatic acid phosphatase (PAP), inhibited by L-tartrate ✓
- C Bone-specific alkaline phosphatase
- D Lysosomal acid phosphatase found in macrophages
Correct answer: B. Prostatic acid phosphatase (PAP), inhibited by L-tartrate
Explanation
Prostatic acid phosphatase (PAP) is the isoenzyme specifically inhibited by L-tartrate, distinguishing it from other acid phosphatase isoenzymes. It is elevated in metastatic prostate carcinoma. TRAP (tartrate-resistant) is the macrophage/osteoclast isoenzyme, elevated in hairy cell leukemia. Bone-specific ALP is an alkaline phosphatase isoenzyme, not acid phosphatase.
Reference: Harper's Illustrated Biochemistry, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.