PKA, pKa, or other similar variations may stand for:
- pKa, the symbol for the acid dissociation constant at logarithmic scale
- Protein kinase A, a class of cAMP-dependent enzymes
- Pi Kappa Alpha, the North-American social fraternity
- Public key authentication, establishing key authenticity in public-key cryptography
- Professional Karate Association
- Primary knock-on atom
- Professionally known as
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