Outline of the Taxol biosynthetic pathway. The cyclization of
geranylgeranyl diphosphate to taxadiene by taxadiene synthase and the
hydroxylation to taxadien-5α-ol by taxadiene 5α-hydroxylase
(a), the acetylation of taxadien-5α-ol by
taxa-4(20),11(12)-dien-5α-ol O-acetyltransferase (TAT)
(b), the conversion of a 2-debenzoyl “taxoid-type”
intermediate to 10-deacetylbaccatin III by a taxane
2α-O-benzoyltransferase (TBT) (c), the
conversion of 10-deacetylbaccatin III to baccatin III by
10-deacetylbaccatin III 10-O-acetyltransferase (DBAT)
(d), and the side-chain attachment to baccatin III to form
Taxol (e) are illustrated. The broken arrow indicates
several as-yet-undefined steps.