Identification of a Polyketide Synthase Involved in Sorbicillin Biosynthesis by Penicillium chrysogenum

Abstract

Secondary metabolism in Penicillium chrysogenum was intensively subjected to classical strain improvement (CSI), the resulting industrial strains producing high levels of ␤-lactams. During this process, the production of yellow pigments, including sorbicillinoids, was eliminated as part of a strategy to enable the rapid purification of ␤-lactams. Here we report the identification of the polyketide synthase (PKS) gene essential for sorbicillinoid biosynthesis in P. chrysogenum. We demonstrate that the production of polyketide precursors like sorbicillinol and dihydrosorbicillinol as well as their derivatives bisorbicillinoids requires the function of a highly reducing PKS encoded by the gene Pc21g05080 (pks13). This gene belongs to the cluster that was mutated and transcriptionally silenced during the strain improvement program. Using an improved ␤-lactam-producing strain, repair of the mutation in pks13 led to the restoration of sorbicillinoid production. This now enables genetic studies on the mechanism of sorbicillinoid biosynthesis in P. chrysogenum and opens new perspectives for pathway engineering. IMPORTANCESorbicillinoids are secondary metabolites with antiviral, anti-inflammatory, and antimicrobial activities produced by filamentous fungi. This study identified the gene cluster responsible for sorbicillinoid formation in Penicillium chrysogenum, which now allows engineering of this diverse group of compounds.

Thioester reduction and aldehyde transamination are universal steps in actinobacterial polyketide alkaloid biosynthesis

“…4,24–26 TR-catalysed reductive chain release has also been proposed to occur in several fungal PKS systems, although direct biochemical evidence for this is currently lacking. 27–31 In contrast, relatively few bacterial modular PKSs have been reported, prior to this work, to contain a TR domain and to the best of our knowledge CpkC-TR is the first of these to be biochemically characterized. In common with a TR (Zmn14) that we recently showed to be responsible for chain release from a polyunsaturated fatty acid synthase-like assembly line in the biosynthesis of the zeamine antibiotics, 32 CpkC-TR has a strict preference for NADH.…”

Transcription factor Xpp1 is a switch between primary and secondary fungal metabolism

“…The industrially used, cellulase-producing fungus T. reesei secretes a typical yellow pigment on a range of carbon sources (35)(36)(37). The pigment is a mixture of different sorbicillin derivatives, of which biosynthesis results from a gene cluster that is present in a range of not closely related ascomycetes (38,39). However, in a previous study, we cultivated an xpp1 deletion strain and its parent strain on carboxymethylcellulose (CMC) to determine the expression levels of cellulases (33).…”

“…‡ Homolog of P. chrysogenum SorB, which is involved in sorbicillin biosynthesis (38,39). § Homolog of P. chrysogenum SorA, which is essential for sorbicillin biosynthesis (38,39). 73621 from the sorbicillin cluster were increased in the xpp1 deletion compared with the parent strain (Fig.…”

“…The expression levels of the gene coding for PKS (35). ‡ Homolog of P. chrysogenum SorB, which is involved in sorbicillin biosynthesis (38,39). § Homolog of P. chrysogenum SorA, which is essential for sorbicillin biosynthesis (38,39).…”

Diels–Alder Reactions During the Biosynthesis of Sorbicillinoids

“…[9] In subsequent studies,k nockout of sorA by the Dreissen group abolished production of 1 and all related sorbicillinoids. [20] Theonly other confirmed homologous sorbicillinoid BGC exists in T. reesei QM6a [21] and shares the three core genes sorA, sorB and sorC required for formation of 2 (Scheme 1E). [9,[20][21][22] The T. reesei BGC also encodes asecond FMO named SorD.D erntl et al [21] proposed that T. reesei SorD catalyses the oxidation of 1b to 1a (Scheme 1F).…”