obsolete 2-hydroxy-3-carboxy-6-oxo-7-methylocta-2,4-dienoate decarboxylase activity (obsolete GO:0018791)
OBSOLETE. Catalysis of the reaction: 2-hydroxy-3-carboxy-6-oxo-7-methylocta-2,4-dienoate = CO2 + 2-hydroxy-6-oxo-7-methylocta-2,4-dienoate.