Tingting Li

Aminotransferases are promising green biocatalysts for the synthesis of chiral amines, yet their limited catalytic efficiencies restrict broader industrial applications. In this study, a novel (R)-amine transaminase, FalAT, was identified from Fusarium albosuccineum through genome mining. FalAT exhibited optimal activity at 30 °C and pH 7.0 and catalyzed the conversion of 1-Boc-3-piperidone to (R)-1-Boc-3-aminopiperidine with >99 % enantiomeric excess. To efficiently enhance its catalytic performance, a Substrate–Protein Interaction Network (SPIN) strategy was implemented, integrating structure-guided analysis, molecular docking, virtual saturation mutagenesis, and dual energy–distance filtering. SPIN first screened and constructed a mutational library covering 70 amino acid positions, which was subsequently narrowed to 9 key residues, ultimately yielding 15 candidate mutants for experimental validation. Experimental results showed that five mutants exhibited higher catalytic activity than the wild-type enzyme, among which R126A was the most effective, displaying approximately a 4-fold increase in catalytic activity and a 13-fold enhancement in catalytic efficiency (k_cat/K_m = 2.05 s⁻¹ mM⁻¹). Molecular dynamics simulations revealed that the R126A mutation expanded the active-site cavity, alleviated steric hindrance, and strengthened hydrophobic interactions, thereby improving substrate binding and catalytic turnover. Furthermore, substrate profiling demonstrated that FalAT possesses moderate substrate promiscuity. Overall, the SPIN strategy significantly improved the catalytic performance of FalAT while markedly reducing experimental workload, providing an efficient and generalizable approach for the directed evolution of (R)-amine transaminases for the green synthesis of chiral amines.

Chiral amines, as essential chiral building blocks in drug synthesis, present a considerable challenge in biomanufacturing due to the requirement for highly efficient stereoselective synthesis. In this study, we successfully cloned and heterologously expressed a novel (R)-amine transaminase, MagAT, from Mycolicibacterium agri. Systematic analysis showed optimal activity at pH 7.0, with the highest reaction rate occurring within 30 min at 50 ℃. However, considering overall thermal stability, 40℃ was selected as the operating temperature for subsequent experiments. Furthermore, the enzyme retained nearly 100% catalytic activity in the presence of 10% methanol, DMSO, and chloroform. Kinetic analysis demonstrated that MagAT possessed high substrate affinity, with Michaelis constants (K_m) of 5.13 ± 0.45 mM for (R)-1-phenylethan-1-amine and 3.73 ± 0.34 mM for pyruvate. Substrate specificity studies indicated that MagAT efficiently catalyzed the conversion of C3-C8 aliphatic amines (e.g., (R)-2-aminooctane) and monocyclic aromatic amines (e.g., (R)-1-phenylethan-1-amine), whereas its catalytic activity significantly declined for sterically hindered substrates such as naphthylamine. 3D structural modeling with AlphaFold3 and molecular docking showed that steric hindrance from key residues in the O-pocket critically influences substrate specificity. This study not only provides an efficient biocatalyst for the biosynthesis of chiral amines but also establishes a theoretical basis for the rational design of transaminases with broader substrate adaptability.

Chiral amines are vital structural motifs in pharmaceuticals and agrochemicals, where enantiomeric purity governs bioactivity and environmental behavior. We identified a novel (R)-selective amine transaminase (MwoAT) from Mycobacterium sp. via genome mining, which exhibits activity toward the synthesis of the chiral amine (R)-1-methyl-3-phenylpropylamine. The enzyme displayed optimal activity at pH 7.0 and 40 °C, with high thermostability and solvent tolerance. Using an AlphaFold3-guided semi-rational engineering strategy integrating molecular docking, alanine scanning, and saturation mutagenesis, residue L175 was pinpointed as critical for substrate binding. The resulting L175G variant exhibited a 2.1-fold increase in catalytic efficiency (k_cat/K_m) and improved thermal stability. Applied to the asymmetric synthesis of (R)-1-methyl-3-phenylpropylamine—a precursor for the antihypertensive drug dilevalol and potential scaffold for crop protection agents—the mutant achieved 26.4% conversion with ≥99.9% ee. The enzyme also accepted several ketones relevant to agrochemical synthesis, underscoring its versatility. This work delivers an engineered biocatalyst for sustainable chiral amine production and demonstrates an AI-assisted protein engineering framework applicable to both medicinal and agricultural chemistry.

A yet unidentified branched‐chain transaminase (BCAT), ApBCAT, was identified in the thermostable Aeribacillus pallidus . Notably, ApBCAT exhibits exceptional thermal stability and demonstrates the ability to catalyze a wide range of natural and unnatural amino acids. This combination of broad substrate spectrum and thermal resistance is unusual in the BCAT family, indicating the promising industrial potential of ApBCAT.

Seed germination is a complex process that is regulated by various exogenous and endogenous factors, in which abscisic acid (ABA) plays a crucial role. The triphosphate tunnel metalloenzyme (TTM) superfamily exists in all living organisms, but research on its biological role is limited. Here, we reveal that TTM2 functions in ABA-mediated seed germination. Our study indicates that TTM2 expression is enhanced but repressed by ABA during seed germination. Promoted TTM2 expression in 35S::TTM2-FLAG rescues ABA-mediated inhibition of seed germination and early seedling development and ttm2 mutants exhibit lower seed germination rate and reduced cotyledon greening compared with the wild type, revealing that the repression of TTM2 expression is required for ABA-mediated inhibition of seed germination and early seedling development. Further, ABA inhibits TTM2 expression by ABA insensitive 4 (ABI4) binding of TTM2 promoter and the ABA-insensitive phenotype of abi4-1 with higher TTM2 expression can be rescued by mutation of TTM2 in abi4-1 ttm2-1 mutant, indicating that TTM2 acts downstream of ABI4. In addition, TTM1, a homolog of TTM2, is not involved in ABA-mediated regulation of seed germination. In summary, our findings reveal that TTM2 acts as a downstream factor of ABI4 in ABA-mediated seed germination and early seedling growth.

Regulation of seed germination is important for plant survival and propagation. ABSCISIC ACID (ABA) INSENSITIVE5 (ABI5), the central transcription factor in the ABA signaling pathway, plays a fundamental role in the regulation of ABA-responsive gene expression during seed germination; however, how ABI5 transcriptional activation activity is regulated remains to be elucidated. Here, we report that C-type Cyclin1;1 (CycC1;1) is an ABI5-interacting partner affecting the ABA response and seed germination in Arabidopsis (Arabidopsis thaliana). The CycC1;1 loss-of-function mutant is hypersensitive to ABA, and this phenotype was rescued by mutation of ABI5. Moreover, CycC1;1 suppresses ABI5 transcriptional activation activity for ABI5-targeted genes including ABI5 itself by occupying their promoters and disrupting RNA polymerase II recruitment; thus the cycc1;1 mutant shows increased expression of ABI5 and genes downstream of ABI5. Furthermore, ABA reduces the interaction between CycC1;1 and ABI5, while phospho-mimic but not phospho-dead mutation of serine-42 in ABI5 abolishes CycC1;1 interaction with ABI5 and relieves CycC1;1 inhibition of ABI5-mediated transcriptional activation of downstream target genes. Together, our study illustrates that CycC1;1 negatively modulates the ABA response by interacting with and inhibiting ABI5, while ABA relieves the CycC1;1 interaction with and inhibition of ABI5 to activate ABI5 activity for the ABA response, thereby inhibiting seed germination.