Struktur der Sulfoxid-Synthase EgtB aus der Ergothionein- Biosynthese

Recent Strategies for the Biosynthesis of Ergothioneine

Ergothioneine (EGT) is a unique naturally occurring amino acid that is usually biosynthesized by bacteria and fungi. As a food-derived antioxidant and cytoprotectant, it has several physiological benefits and has a wide range of applications in food, medicine, and cosmetics. Traditional production of EGT is mainly through biological extraction or chemical synthesis; however, these methods are inefficient, making large-scale production to meet the growing market demand difficult. Nowadays, the rapid development of synthetic biology has greatly accelerated the research on the EGT production by microbial fermentation. In this paper, the biological characteristics, applications, biosynthesis, separation, and detection methods of EGT were fully reviewed. Furthermore, the approaches and challenges for engineering microbial cells to efficiently synthesize EGT were also discussed. This work provides new ideas and future research potentials in EGT production.

Convergent Evolution of Fungal Cysteine Dioxygenases

Cupin-type cysteine dioxygenases (CDOs) are non-heme iron enzymes that occur in animals, plants, bacteria and in filamentous fungi. In this report, we show that agaricomycetes contain an entirely unrelated type of CDO that emerged by convergent evolution from enzymes involved in the biosynthesis of ergothioneine. The activity of this CDO type is dependent on the ergothioneine precursor N-α-trimethylhistidine. The metabolic link between ergothioneine production and cysteine oxidation suggests that the two processes might be part of the same chemical response in fungi, for example against oxidative stress.

Selenocysteine as a Substrate, an Inhibitor and a Mechanistic Probe for Bacterial and Fungal Iron-Dependent Sulfoxide Synthases

Sulfoxide synthases are non-heme iron enzymes that participate in the biosynthesis of thiohistidines, such as ergothioneine and ovothiol A. The sulfoxide synthase EgtB from Chloracidobacterium thermophilum (CthEgtB) catalyzes oxidative coupling between the side chains of N-α-trimethyl histidine (TMH) and cysteine (Cys) in a reaction that entails complete reduction of molecular oxygen, carbon-sulfur (C-S) and sulfur-oxygen (S-O) bond formation as well as carbon-hydrogen (C-H) bond cleavage. In this report, we show that CthEgtB and other bacterial sulfoxide synthases cannot efficiently accept selenocysteine (SeCys) as a substrate in place of cysteine. In contrast, the sulfoxide synthase from the filamentous fungus Chaetomium thermophilum (CthEgt1) catalyzes C-S and C-Se bond formation at almost equal efficiency. We discuss evidence suggesting that this functional difference between bacterial and fungal sulfoxide synthases emerges from different modes of oxygen activation.