Figure 4: Proposed biosynthetic mechanism for formation of the four tetramic acid-containing macrolactams. | Nature Communications

Figure 4: Proposed biosynthetic mechanism for formation of the four tetramic acid-containing macrolactams.

From: Activation and characterization of a cryptic polycyclic tetramate macrolactam biosynthetic gene cluster

Figure 4

The PKS is responsible for the hexaketide chain synthesis and works together with the NRPS to condense the two polyketide chains with ornithine. The formation of the first polycyclic ring is catalysed by SGR812 and the second ring is closed by SGR813. Compound c is the key intermediate that can be converted into compound a by SGR815 or compound b by SGR810/SGR811. A shunt product compound d will be formed if SGR813 is absent in the cluster. SEnz is the carrier protein within the PKS or NRPS. The red structures are the ones with full set of NMR data.

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