Kuniki Kino

When treated with various compounds, fungi exhibit characteristic morphological changes depending on their mode of action. Previously, we constructed morphology-based databases of the rice blast fungus Pyricularia oryzae and human pathogenic fungus Candida albicans and used them for antifungal screening. As these databases are manually created by human experts, objectivity and throughput may be a concern. To overcome these limitations, we developed a new artificial intelligence (AI)-based automated classification system for morphological changes in the filamentous fungus Aspergillus oryzae. Using this system, we screened a library of 7602 microbial broths and found that the culture broth of Streptomyces sp. RK21-A1205 exhibited potent antifungal activity and induced unique morphological changes distinct from those induced by conventional antifungal agents. Antifungal-activity-guided purification yielded the active metabolite RK-1205-I (1), whose chemical structure was identified as a new fostriecin derivative. 1 showed strong growth inhibitory activity against A. oryzae and other fungi, including A. fumigatus and C. auris, with IC₅₀ value of 0.020 and 0.21 µM, respectively. Furthermore, 1 inhibited protein phosphatase 2A (PP2A) activity in the fungal cells. This study demonstrates that our newly developed AI-based phenotypic screening system can effectively distinguish morphological changes induced by microbial broths and facilitates the identification of novel antifungal compounds.

Candida albicans exhibits a unique dimorphic behavior, allowing it to switch between unicellular budding yeast and filamentous hyphal growth. This dimorphism is crucial for its pathogenicity, influencing processes such as adhesion, invasion, immune evasion, and host response. A comprehensive understanding of the molecular mechanisms governing yeast and hyphal growth, as well as the switch between these forms, is crucial for the development of effective anticandidal therapies. In this study, we screened for small molecules that interfere with the dimorphism of C. albicans and identified the actinomycete metabolite RK-276A/SF2768 as a potent inhibitor of this process. Time-lapse microscopy revealed that SF2768 inhibited hyphal branching and lateral yeast budding during the hyphal-to-yeast transition. Interestingly, SF2768 also suppressed farnesol-induced yeast growth by inhibiting yeast bud formation. The effects of SF2768 were canceled with copper addition, and other copper chelators, such as trientine and d -penicillamine, induced similar phenotypes, indicating that the copper-chelating activity of SF2768 is crucial for its antifungal properties. Furthermore, copper ions induced both hyphal and yeast bud formation. These findings strongly suggest that copper ions play a role in Candida budding, and the copper chelators could be developed as novel antifungal agents against not only dimorphic Candida spp. but also non-dimorphic Candida spp.

Vanillin is one of the world’s most important flavor and fragrance compounds used in foods and cosmetics. In plants, vanillin is reportedly biosynthesized from ferulic acid via the hydratase/lyase-type enzyme VpVAN. However, in biotechnological and biocatalytic applications, the use of VpVAN limits the production of vanillin. Although microbial enzymes are helpful as substitutes for plant enzymes, synthesizing vanillin from ferulic acid in one step using microbial enzymes remains a challenge. Here, we developed a single enzyme that catalyzes vanillin production from ferulic acid in a coenzyme-independent manner via the rational design of a microbial dioxygenase in the carotenoid cleavage oxygenase family using computational simulations. This enzyme acquired catalytic activity toward ferulic acid by introducing mutations into the active center to increase its affinity for ferulic acid. We found that the single enzyme can catalyze not only the production of vanillin from ferulic acid but also the synthesis of other aldehydes from p -coumaric acid, sinapinic acid, and coniferyl alcohol. These results indicate that the approach used in this study can greatly expand the range of substrates available for the dioxygenase family of enzymes. The engineered enzyme enables efficient production of vanillin and other value-added aldehydes from renewable lignin-derived compounds. IMPORTANCE: The final step of vanillin biosynthesis in plants is reportedly catalyzed by the enzyme VpVAN. Prior to our study, VpVAN was the only reported enzyme that directly converts ferulic acid to vanillin. However, as many characteristics of VpVAN remain unknown, this enzyme is not yet suitable for biocatalytic applications. We show that an enzyme that converts ferulic acid to vanillin in one step could be constructed by modifying a microbial dioxygenase-type enzyme. The engineered enzyme is of biotechnological importance as a tool for the production of vanillin and related compounds via biocatalytic processes and metabolic engineering. The results of this study may also provide useful insights for understanding vanillin biosynthesis in plants.

Imidazole dipeptides, histidine-containing dipeptides, including carnosine (β-alanyl-l-histidine), anserine (β-alanyl-3-methyl-l-histidine), and balenine (β-alanyl-1-methyl-l-histidine) in animal muscles have physiological functions, such as significant antioxidant and antifatigue effects. They are obtained by extraction from natural raw materials, including chicken and fish meat. However, using natural raw materials entails stable supply and mass production limitations. l-amino acid α-ligase (Lal) catalyzes the formation of various dipeptides from unprotected l-amino acids by conjugating with adenosine 5'-triphosphate (ATP) hydrolysis reaction. In this study, site-directed mutagenesis of Lal was applied to establish an efficient method for producing imidazole dipeptides by the enzymatic process. We significantly improved the conversion rate from substrate amino acids compared with wild-type Lal.

2,5-Diketopiperazine (DKP) is a cyclic peptide composed of two amino acids and has been recently reported to exhibit various biological activities. DKPs ha

Owing to an increasing concern for sustainability, enzymatic approaches for producing industrially useful compounds have attracted considerable attention as a powerful complement to chemical synthesis for environment-friendly synthesis. In this study, we developed a bioproduction method for β-hydroxy-α-amino acid synthesis using a newly discovered enzyme.

Owing to carboxylation activity, reversible decarboxylases can use CO₂ as a C1-building block to produce useful carboxylic acids. Although many reversible decarboxylases can synthesize aromatic monocarboxylic acids, only a few reversible decarboxylases have been reported to date that catalyze the synthesis of aromatic dicarboxylic acids. In the present study, a reversible 4-hydroxyisophthalic acid decarboxylase was identified in Cystobasidium slooffiae HTK3. Furthermore, recombinant 4-hydroxyisophthalic acid decarboxylase was prepared, characterized, and used for 4-hydroxyisophthalic acid production from 4-hydroxybenzoic acid.