Catalyzes the decarboxylation of L-tyrosine to produce tyramine for methanofuran biosynthesis. Can also catalyze the decarboxylation of L-aspartate to produce beta-alanine for coenzyme A (CoA) biosynthesis. H(+) + L-tyrosine = CO2 + tyramine H(+) + L-aspartate = beta-alanine + CO2 Cofactor biosynthesis; methanofuran biosynthesis. Cofactor biosynthesis; coenzyme A biosynthesis. Belongs to the group II decarboxylase family. MfnA subfamily.