Recent advances of activation techniques-based discovery of new compounds from marine fungi.

Natural products have been playing an indispensable role in drug discovery. However, it seems that the golden period of discovering new compounds has passed since the first antibiotic-penicillin. With the development of genome sequencing, it has been found that marine fungi contain various biosynthetic gene clusters (BGCs), which are silent under standard laboratory conditions. Therefore, it might be envisioned that once these BGCs are expressed, a large quantity of new secondary metabolites with biological activities could be generated. This paper reviewed several activation techniques implemented from 2020 to 2022, including epigenetics regulation, co-culture, precursor feeding, heterologous expression, and changing fermentation parameters to activate silent BGCs of marine fungi. We also described the diversity and bioactivities of these newly discovered uncommon marine fungi-derived compounds based on the classification of activation techniques, facilitating research groups focusing on natural products to enhance discovering efficiency.

Identification and characterization of L-lysine decarboxylase from Huperzia serrata and its role in the metabolic pathway of lycopodium alkaloid.

Lysine decarboxylation is the first biosynthetic step of Huperzine A (HupA). Six cDNAs encoding lysine decarboxylases (LDCs) were cloned from Huperzia serrata by degenerate PCR and rapid amplification of cDNA ends (RACE). One HsLDC isoform was functionally characterized as lysine decarboxylase. The HsLDC exhibited greatest catalytic efficiency (kcat/Km, 2.11 s-1 mM-1) toward L-lysine in vitro among all reported plant-LDCs. Moreover, transient expression of the HsLDC in tobacco leaves specifically increased cadaverine content from zero to 0.75 mg per gram of dry mass. Additionally, a convenient and reliable method used to detect the two catalytic products was developed. With the novel method, the enzymatic products of HsLDC and HsCAO, namely cadaverine and 5-aminopentanal, respectively, were detected simultaneously both in assay with purified enzymes and in transgenic tobacco leaves. This work not only provides direct evidence of the first two-step in biosynthetic pathway of HupA in Huperzia serrata and paves the way for further elucidation of the pathway, but also enables engineering heterologous production of HupA.