Catalyzes the decarboxylation of L-aspartate, 3-sulfino-L-alanine (cysteine sulfinic acid), and L-cysteate to beta-alanine, hypotaurine and taurine, respectively. The preferred substrate is L-aspartate. Does not exhibit any decarboxylation activity toward glutamate. H(+) + L-aspartate = beta-alanine + CO2 3-sulfino-L-alanine + H(+) = CO2 + hypotaurine Homodimer. Belongs to the group II decarboxylase family.