Biosynthetic gene-based secondary metabolite screening: a new diterpene, methyl phomopsenonate, from the fungus Phomopsis amygdali.

The presence of the geranylgeranyl diphosphate synthase (GGS) gene is a common feature of gene clusters for diterpene biosynthesis. We demonstrated identification of a diterpene gene cluster using homology-based PCR of GGS genes and the subsequent genome walking in the fungus Phomopsis amygdali N2. Structure determination of a novel diterpene hydrocarbon phomopsene provided by enzymatic synthesis with the recombinant terpene synthase PaPS and screening of fungal broth extracts with reference to characteristic NMR signals of phomopsene allowed us to isolate a new diterpene, methyl phomopsenonate. The versatility of the gene-based screening of unidentified diterpenes is discussed in regard to fungal genomic data.

Purulent Pericarditis with Salmonella enterica Subspecies arizona in a Patient with Type 2 Diabetes Mellitus.

Purulent pericarditis is a life-threatening disorder, even in the modern antibiotic era. Although diabetes mellitus is known to be associated with an increased risk of multiple types of infections, purulent pericarditis is extremely rare. We herein report an unusual case of pericarditis caused by Salmonella enterica subspecies arizona that was not associated with any evident underlying immunosuppressive disorder apart from uncontrolled type 2 diabetes mellitus. Because a pet snake was suspected as being the source of infection in the present case, patient education and a detailed review of exposure history could play an important role in treating patients with diabetes mellitus.

Fusicoccins are biosynthesized by an unusual chimera diterpene synthase in fungi.

Fusicoccins are a class of diterpene glucosides produced by the plant-pathogenic fungus Phomopsis amygdali. As modulators of 14-3-3 proteins, fusicoccins function as potent activators of plasma membrane H(+)-ATPase in plants and also exhibit unique biological activity in animal cells. Despite their well studied biological activities, no genes encoding fusicoccin biosynthetic enzymes have been identified. Cyclic diterpenes are commonly synthesized via cyclization of a C(20) precursor, geranylgeranyl diphosphate (GGDP), which is produced through condensation of the universal C(5) isoprene units dimethylallyl diphosphate and isopentenyl diphosphate by prenyltransferases. We found that (+)-fusicocca-2,10 (14)-diene, a tricyclic hydrocarbon precursor for fusicoccins, is biosynthesized from the C(5) isoprene units by an unusual multifunctional enzyme, P. amygdali fusicoccadiene synthase (PaFS), which shows both prenyltransferase and terpene cyclase activities. The functional analysis of truncated mutants and site-directed mutagenesis demonstrated that PaFS consists of two domains: a terpene cyclase domain at the N terminus and a prenyltransferase domain at the C terminus. These findings suggest that fusicoccadiene can be produced efficiently in the fungus by using the C(5) precursors, irrespective of GGDP availability. In fact, heterologous expression of PaFS alone resulted in the accumulation of fusicocca-2,10 (14)-diene in Escherichia coli cells, whereas no product was detected in E. coli cells expressing Gibberella fujikuroi ent-kaurene synthase, another fungal diterpene cyclase that also uses GGDP as a substrate but does not contain a prenyltransferase domain. Genome walking suggested that fusicoccin biosynthetic enzymes are encoded as a gene cluster near the PaFS gene.

Novel gamma-secretase inhibitors discovered by library screening of in-house synthetic natural product intermediates.

Screening of our in-house compound library comprised of intermediates of natural product synthesis projects resulted in discovering two novel gamma-secretase inhibitors, which coincidently had similar moieties, that is, cyclohexenone and two aryl groups arranged on the core six-membered ring. Structure-activity relationship studies of these compounds were also developed.