Catalyzes the decarboxylation of L-cysteine to cysteamine and of 3-sulfino-L-alanine (cysteine sulfinic acid) to hypotaurine (PubMed:17420004, Ref.2, Ref.3, PubMed:29796005). Also catalyzes the decarboxylation of various amino acids such as L-lysine, L-glutamate, L-asparaginate and L-proline (Ref.2). In vitro, shows highest activity with L-cysteine as substrate (Ref.2). H(+) + L-cysteine = CO2 + cysteamine 3-sulfino-L-alanine + H(+) = CO2 + hypotaurine Slightly stimulated in the presence of 1 mM Mg(2+). kcat is 4.57 min(-1) with L-cysteine as substrate (Ref.2). kcat is 45.8 min(-1) with L-cysteine sulfinic acid as substrate (Ref.3). Optimum pH is 7.0. Optimum temperature is 35 degrees Celsius. In the N-terminal section; belongs to the HFCD (homo-oligomeric flavin containing Cys decarboxylase) superfamily. In the C-terminal section; belongs to the PPC synthetase family.