Catalyzes three successive oxidations of ent-kaurenoic acid giving gibberellin 12 (GA12), a key step in gibberellins (GAs) biosynthesis. GAs, which are involved many processes, including stem elongation, play a central role in plant development. ent-kaur-16-en-19-oate + 3 O2 + 3 reduced [NADPH--hemoprotein reductase] = gibberellin A12 + 4 H(+) + 4 H2O + 3 oxidized [NADPH--hemoprotein reductase] Plant hormone biosynthesis; gibberellin biosynthesis. Widely expressed. Highly expressed in influorescence stem, influorescence, and silique tissue. Weakly expressed in cauline and rosette leaves. Expressed at a weaker level in stem and influorescence than AtKAO1/CYP88A3. Belongs to the cytochrome P450 family.