Schematic of the thuringiensin biosynthesis pathways. Step 1, synthesis of key precursor gluconic diacid (precursor A) by thuA, thuC, and thuD; step 2, assembly of gluconic diacid, glucose, and adenosine by thuF and thu1; step 3, phosphorylation of precursor C by ThuE. Numbers have been added to designate the molecular weight of each intermediate.