FIGURE 1.

The S. clavuligerus clavulanic acid and 5S clavam biosynthetic pathways. The pathway is depicted in three parts: the central green box represents the steps shared between CA and 5S clavam biosynthesis, whereas the pink (left) and yellow (right) boxes indicate the late steps specific for CA or 5S clavam production, respectively. The solid arrows represent known reactions and broken arrows indicate uncharacterized steps, which could potentially involve more than one unknown gene product/enzyme. The names of core biosynthetic enzymes (blue) catalyzing known reactions and the respective gene(s) encoding them (red) are included where applicable. The stereochemistries (R/S) of the intermediates/products are also included along with their names. The identities of the gene clusters involved in each stage of biosynthesis is indicated at the bottom of the figure. Note that the shared part of the pathway (green) involves substitutable isozymes (CeaS, Bls, Cas, and Pah), which are encoded by two sets of genes (1 and 2) residing in three separate gene clusters. Additional genes from the respective clusters for which exact biosynthetic functions have not been assigned are not shown to simply interpretation.