Biology subjects

Topakas, E.

Publications and source records attributed to Topakas, E..

5 recordsLinked to original sources

bioRxiv2026

Synthetic biology-guided modular engineering of the secreted cutinase FoCut5a with a carbohydrate-binding module improves poly(ester-urethane) depolymerization in Yarrowia lipolytica

Poly(ester-urethane) bioconversion requires efficient polymer-degrading enzymes and microbial hosts capable of processing the resulting monomers. However, the optimal modular design of secreted cutinases for depolymerizing insoluble polyester-polyurethanes remains largely unexplored. Here, we established a combinatorial synthetic biology strategy in Yarrowia lipolytica based on the fungal cutinase FoCut5a from Fusarium oxysporum. A library of 96 Golden Gate-assembled constructs, combining four secretion signals, four interdomain linkers, and six substrate-binding domains, was integrated site-specifically into the genome and screened for depolymerization of the polyester-polyurethane dispersion Impranil DLN-SD. The best-performing variant fused FoCut5a to the carbohydrate-binding module TrCBM1. LC-MS analysis demonstrated release of adipic acid, 1,6-hexanediol, and neopentyl glycol, confirming ester-bond hydrolysis within the polyester domains of the polymer and additionally detected 6-hydroxycaproate, indicating oxidation of polyurethane-derived 1,6-hexanediol by Y. lipolytica. Purified FoCut5a-TrCBM1 displayed unchanged activity on p-nitrophenyl butyrate but reduced Impranil turbidity 5.6-fold faster and increased release of 1,6-hexanediol and adipic acid by 76-fold and 220-fold, respectively, compared to the unfused enzyme. These results highlight modular enzyme engineering as an effective strategy to enhance polyester-polyurethane deconstruction and support Y. lipolytica as a platform for polymer bioconversion and upcycling.

synthetic biology↗

bioRxiv2026

Structural investigation of an engineered feruloyl esterase with improved MHET degrading properties

MHETases are enzymes implicated in polyethylene terephthalate (PET) biodegradation. The present study elucidates the structural determinants that result in increased mono(2-hydroxyethyl) terephthalate (MHET) degradation by a feruloyl esterase, which has been engineered to resemble MHETase active site. The crystal structures of the variant in apo and benzoic acid bound state reveal the changes induced by the introduced mutation, specifically the formation of a hydrogen bond and a trans to cis isomerization of a peptide bond in the vicinity of the catalytic site. Molecular dynamics simulations demonstrate the stabilization of the loop harboring the engineered residue, as well as an expansion of the substrate binding cleft, which would facilitate accommodation of a broader variety of substrates, indicative of a promiscuous biocatalyst. EnzymeEnzyme Commission Number: EC 3.1.1.73; Uniprot accession code: A0A1D3S5H0_FUSOX

biochemistry↗

bioRxiv2025

The C-terminal intrinsically disordered region of a fungal LPMO binds copper and displays anti-fungal properties

Lytic Polysaccharide Monooxygenases (LPMOs) are enzymes that play a crucial role in the degradation of complex polysaccharides such as cellulose and chitin. While LPMOs have attracted significant interest for industrial applications to convert biomass into biofuels, emerging evidence suggests alternative functions in fungal plant pathogenesis, microbial diseases and (micro)organism development. The AA14 LPMO family is widely distributed in filamentous fungi but remains enigmatic as its initially-suspected substrate specificity was recently challenged. In this study, we investigated the disordered C-terminal regions (dCTRs), found in more than half of AA14 family members and hypothesized to have functional relevance. Focusing on the Pycnoporus coccineus AA14A LPMO, we used small angle X-ray scattering (SAXS) and circular dichroism to show that its dCTR is highly disordered. It consists of a heavily glycosylated low complexity region followed by a charged C-terminal tail. We uncovered that the PcoAA14A dCTR binds copper ions through histidine residues located in the C-terminal tail. Using electron paramagnetic resonance (EPR), we further demonstrated that dimer formation occurs through an oxidative process involving copper and a redox-sensitive cysteine. Noting similarities between the last residues of the C-terminal tail and antimicrobial peptides, we investigated its potential antimicrobial function. We found that the positively charged region of the C-terminal tail selectively inhibits the growth of basidiomycete fungal spores. These data reveal that the dCTRs appended to AA14 LPMOs are functional regions that must be considered to unveil the role of these atypical LPMOs. Significance StatementLytic polysaccharide monooxygenases (LPMOs) degrade complex polysaccharides and are central to biomass conversion. Their biological relevance is expanding, with emerging roles in fungal development and host interactions. Despite this broad potential, research has largely focused on their catalytic domain. One area that remains poorly understood is the function of their C-terminal region, predicted to be intrinsically disordered (dCTR). The AA14 LPMO family, whose substrate specificity remains enigmatic, is enriched in dCTRs. This study provides the first experimental evidence of the disordered nature of the dCTR of an AA14 LPMO. Using multidisciplinary approaches, we demonstrate that the dCTR binds metals and exhibits antifungal activity. These findings establish dCTRs as functional regions, essential for understanding the biological roles of LPMOs.

biochemistry↗

bioRxiv2024

Multi-omics insights into the response of Aspergillus parasiticus to long-chain alkanes in relation to polyethylene degradation

Plastic pollution presents a global challenge, with polyethylene (PE) being among the most persistent plastics due to its durability and environmental resilience. In this study, we employed a multi-omics approach to study the ability of Aspergillus parasiticus MM36, an isolate derived from Tenebrio molitor intestines, to metabolize long-chain alkanes (lcAlk) and secrete enzymes able to modify PE. The fungus was grown with hexadecane (C16) or a mixture of lcAlk (C24 to C36) as carbon sources and culture supernatants were tested daily for their ability to modify PE. Proteomic analysis identified induced oxidases potentially involved in lcAlk and PE functionalization. Key enzymes include multicopper oxidases, peroxidases, an unspecific peroxygenase and FAD-dependent monooxygenases. Surfactant proteins facilitating enzymatic and cellular interaction with hydrophobic PE and lcAlk, such as one hydrophobin, three hydrophobic surface-binding proteins (HsbA) and one cerato platanin, were present in all secretomes. Transcriptomic analysis comparing lcAlk to C16 cultures highlighted the enrichment of oxidoreductase activities and carboxylic acid metabolism in both lcAlk incubation days, with transmembrane transporters and transferases predominating on day 2 and biosynthetic processes on day 3. In C16 cultures, hydrolytic enzymes, including esterases, were upregulated alongside Baeyer-Villiger monooxygenases, suggesting a shift toward sub-terminal hydroxylation. Integrating transcriptomic and secretomic data, we propose a mechanism for lcAlk assimilation by A. parasiticus MM36, involving extracellular oxyfunctionalization, hydrocarbon uptake via surface-modifying proteins and channeling through membrane transporters for energy consumption and biosynthetic processes. This study provides insights into fungal mechanisms for alkane metabolism and highlights their relevance to plastic degradation. ImportancePlastic pollution presents a global challenge to marine life and human health, with polyethylene (PE) being among the most persistent plastics due to its durability and environmental resilience. Hydroxylation is regarded as the initial step of PE degradation, similar to alkane oxidation, making alkane-degrading microbes a promising source of plastic degraders. In this study, we used a multi-omics approach to investigate the ability of Aspergillus parasiticus MM36 to metabolize long-chain alkanes and secrete enzymes that modify PE. Proteomic analysis of the secretomes identified key oxidases and biosurfactants that enable the fungus to interact with and transform hydrophobic substrates like PE. Transcriptomic analysis further revealed biological processes involved in alkane assimilation and metabolism. By integrating these insights, we propose a mechanism for fungal alkane metabolism and highlight its relevance to plastic biodegradation. This work advances our understanding of fungal contributions to addressing hydrocarbon and plastic pollution.

microbiology↗

bioRxiv2021

Considerations on activity determinants of fungal polyphenol oxidases based on mutational and structural studies

Polyphenol oxidases (PPOs) are an industrially relevant family of enzymes, being involved in the post-harvest browning of fruits and vegetables, as well as in human melanogenesis. Their involvement lies in their ability to oxidize phenolic or polyphenolic compounds, that subsequently form pigments. PPO family includes tyrosinases and catechol oxidases, which in spite of their high structural similarity, exhibit different catalytic activities. Long-standing research efforts have not yet managed to decipher the structural determinants responsible for this differentiation, as every new theory is disproved by a more recent study. In the present work, we combined biochemical along with structural data, in order to rationalize the function of a previously characterized PPO from Thermothelomyces thermophila (TtPPO). The crystal structure of a TtPPO variant, determined at 1.55 [A] resolution, represents the second known structure of an ascomycete PPO. Kinetic data of structure-guided mutants prove the implication of "gate" residue L306, residue HB1+1 (G292) and HB2+1 (Y296) in TtPPO function against various substrates. Our findings demonstrate the role of L306 in the accommodation of bulky substrates and that residue HB1+1 is unlikely to determine monophenolase activity as suggested from previous studies. IMPORTANCEPPOs are enzymes of biotechnological interest. They have been extensively studied both biochemically and structurally, with a special focus on the plant-derived counterparts. Even so, explicit description of the molecular determinants of their substrate specificity is still pending. Especially for ascomycete PPOs, only one crystal structure has been determined so far, thus limiting our knowledge on this tree branch of the family. In the present study, we report the second crystal structure of an ascomycete PPO. Combined with site-directed mutagenesis and biochemical studies, we depict the amino acids in the vicinity of the active site that affect enzyme activity, and perform a detailed analysis on a variety of substrates. Our findings improve current understanding of structure-function relations of microbial PPOs, which is a prerequisite for the engineering of biocatalysts of desired properties.

biochemistry↗