Catalyzes the production of 4-hydroxyphenylacetaldehyde (HPAA) directly from L-tyrosine, tyramine not being formed as an intermediate. H(+) + H2O + L-tyrosine + O2 = (4-hydroxyphenyl)acetaldehyde + CO2 + H2O2 + NH4(+) kcat is 4.91 sec(-1) with L-tyrosine as substrate. Belongs to the group II decarboxylase family.