ADE2 (YOR128C, P21264) notes

• AIR carboxylase, step 6. Domain architecture: N-terminal PurK ATP-grasp (IPR005875) + C-terminal class I PurE (IPR033747) [UniProt:P21264].
• Fungal Ade2 (Cryptococcus ortholog) is a two-step enzyme: PurK domain uses AIR + ATP + HCO3- to make N5-CAIR, PurE domain converts N5-CAIR to CAIR PMID:9500840.
• Therefore GO:0004638 / EC 4.1.1.21 (class II direct carboxylation, animal PAICS) is the wrong reaction description; MODIFY to GO:0034028 + GO:0034023. YeastCyc assigns EC 4.1.1.21 (mis-modelled reaction).
• ade2 red pigment from AIR PMID:8939809.
• Nucleobase metabolic process terms (IMP/IBA/ARBA) -> MODIFY to de novo IMP biosynthesis.
• Note: direct S. cerevisiae biochemistry of the two sub-reactions not found in the cache; inference from the Cryptococcus enzyme and domain composition.