Catalyzes the decarboxylation of L-aspartate to produce beta-alanine. In vitro, can also catalyzes the decarboxylation of L-glutamate to produce 4-aminobutanoate, but this activity does not seem necessary in vivo. Shows much higher activity with L-aspartate than with L-glutamate. Does not decarboxylate L-tyrosine. H(+) + L-aspartate = beta-alanine + CO2 Inhibited by hydroxylamine. kcat is 0.80 sec(-1) with aspartate as substrate. kcat is 0.18 sec(-1) with glutamate as substrate. Optimum pH is 8.0. Optimum temperature is 85 degrees Celsius. Cofactor biosynthesis; coenzyme A biosynthesis. Homodimer. Can also form homohexamers. No growth on standard medium. Growth can be restored by the addition of exogenous beta-alanine or coenzyme A, but not by the addition of GABA. Belongs to the group II decarboxylase family. MfnA subfamily.