Bioinformatic prediction of the stereoselectivity of modular polyketide synthase: an update of the sequence motifs in ketoreductase domain.

Polyketides are a major class of natural products, including bioactive medicines such as erythromycin and rapamycin. They are often rich in stereocenters biosynthesized by the ketoreductase (KR) domain within the polyketide synthase (PKS) assembly line. Previous studies have identified conserved motifs in KR sequences that enable the bioinformatic prediction of product stereochemistry. However, the reliability and applicability of these prediction methods have not been thoroughly assessed. In this study, we conducted a comprehensive bioinformatic analysis of 1,762 KR sequences from cis-AT PKSs to reevaluate the residues involved in conferring stereoselectivity. Our findings indicate that the previously identified fingerprint motifs remain valid for KRs in ß-modules from actinobacteria, but their reliability diminishes for KRs from other module types or taxonomic origins. Additionally, we have identified several new motifs that exhibit a strong correlation with the stereochemical outcomes of KRs. These updated fingerprint motifs for stereochemical prediction not only enhance our understanding of the enzymatic mechanisms governing stereocontrol but also facilitate accurate stereochemical prediction and genome mining of polyketides derived from modular cis-AT PKSs.

Transformation from 3D Boron Organic Polymers to 1D Nanorod Arrays: Loading Highly Dispersed Nanometal for Green Catalysis.

The increasing global demands for eco-friendly and low-cost catalysts have propelled the advent of nanosized non-noble-metal catalysts to replace traditional noble metals. In this work, ultrafine NiO nanoparticles were prepared rapidly in situ by the strategy of transforming three-dimensional (3D) metal boron organic polymers (BOPs@Ni2+) to one-dimensional (1D) boron organic polymers (BOPs@Ni) nanorod arrays at room temperature. The 3D BOPs@Ni2+ can be quickly obtained by the interaction of 4,4'-bipyridine with Ni2+ and dodecaborate (B12H122-) in an aqueous solution. When Ni2+ is converted into NiO in situ, 1D BOPs@Ni nanostructure transformation from the 3D BOPs@Ni2+ framework was achieved due to the B-H···π interaction between B12H122- and 4,4'-bipyridine. Furthermore, BOPs@Ni exhibits high catalytic activity and rapid kinetics in the conversion of 4-nitrophenol to 4-aminophenol, and the high stability of 1D nanorod arrays guarantees the catalytic activity of BOP@Ni to barely change under recycling for at least 10 times. BOPs@Ni also exhibits good catalytic performance and high selectivity characteristics in the catalytic reduction of a series of nitrobenzene derivatives. This strategy of using BOPs@Ni2+ for loading self-supporting nanometal not only exhibits a highly efficient catalytic hydrogenation of nitrobenzene and its derivative but also provides an effective technical route for designing self-supported nanometal materials.