Poly(butylene adipate-co-terephthalate) (PBAT), a polyester made of terephthalic acid (TPA), 1,4-butanediol, and adipic acid, is extensively utilized in plastic production and has accumulated globally as environmental waste. Biodegradation is an attractive strategy to manage PBAT, but an effective PBAT-degrading enzyme is required. Here, we demonstrate that cutinases are highly potent enzymes that can completely decompose PBAT films in 48 h. We further show that the engineered cutinases, by applying a double mutation strategy to render a more flexible substrate-binding pocket exhibit higher decomposition rates. Notably, these variants produce TPA as a major end-product, which is beneficial feature for the future recycling economy. The crystal structures of wild type and double mutation of a cutinase from Thermobifida fusca in complex with a substrate analogue are also solved, elucidating their substrate-binding modes. These structural and biochemical analyses enable us to propose the mechanism of cutinase-mediated PBAT degradation.

Significance: To address the unmet clinical need for effectively suppressing estrogen receptor (ER) activity with both de novo resistance and in advanced ER-positive breast cancers that are resistant to standard-of-care antiestrogens, we have developed dual-mechanism ER inhibitors (DMERIs) that employ two distinct ER-targeting moieties. These DMERI elicited noncanonical structural perturbations of the receptor ligand-binding domain and stabilized multiple antagonist substates within the dimer to generate highly efficacious antagonism of proliferation in ER-positive breast cancer cells and in allele-specific resistance models. This work reveals conformational modes by which the activity of ER can be effectively suppressed to block breast cancer proliferation.

The biosynthesis of neurotoxin aetokthonotoxin (AETX) that features a unique structure of pentabrominated biindole nitrile involves a first-of-its-kind nitrile synthase termed AetD, an enzyme that shares very low sequence identity to known structures and catalyzes an unprecedented mechanism. In this study, we resolve the crystal structure of AetD in complex with the substrate 5,7-di-Br-L-Trp. AetD adopts the heme oxygenase like fold and forms a hydrophobic cavity within a helical bundle to accommodate the indole moiety. A diiron cluster comprising two irons that serves as a catalytic center binds to the carboxyl O and the amino N of the substrate. Notably, we demonstrate that the AetD-catalyzed reaction is independent of the bromination of the substrate and also solved crystal structures of AetD in complex with 5-Br-L-Trp and L-Trp. Altogether, the present study reveals the substrate-binding pattern and validates the diiron cluster-comprising active center of AetD, which should provide important basis to support the mechanistic investigations into this class of nitrile synthase.

Endocrine therapy that blocks estrogen receptor signaling has been effective for decades as a primary treatment choice for breast cancer patients expressing the estrogen receptor. However, the issue of drug resistance poses a significant clinical challenge. It is therefore critically important to create new therapeutic agents that can suppress ERα activity, particularly in cases of ESR1 mutations. This review highlights recent efforts in drug development of next generation ER-targeted agents, including oral selective ER degraders, proteolysis-targeting chimera ER degraders, and other innovative molecules, such as complete estrogen receptor antagonists and selective estrogen receptor covalent antagonists. The drug design, efficacy, and clinical trials for each compound are detailed herein.