PKA may refer to: Professionally known as: Pen name Stage persona 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, an atom that is displaced from its lattice site by irradiation Painkiller Already, a podcast featuring FPSRussia Pentax KA-mount, a camera lens mount Non-Latin The Latin letters PKA are visually similar to the Cyrillic acronym , the Russian Federal Space Agency