The application of ketoreductase-based biocatalytic reduction to access optically pure Prelog or anti-Prelog alcohols offers a valuable approach for asymmetric synthesis. Despite this, control of the stereopreferences of ketoreductases as desired remains challenging, since natural ketoreductases usually display Prelog preference and it is difficult to transfer the knowledge from engineered anti-Prelog ketoreductases to the others. Here, we present the discovery of a switch between Prelog and anti-Prelog reduction toward halogen-substituted acetophenones in six short-chain dehydrogenase/reductases (SDRs). Through carefully analysis of the structural information and multiple-sequence alignment of several reported SDRs with Prelog or anti-Prelog stereopreference, the key residues that might control their stereopreferences were identified using Lactobacillus fermentum short-chain dehydrogenase/reductase 1 (LfSDR1) as the starting enzyme. Protein engineering at these positions of LfSDR1 could improve its anti-Prelog stereoselectivity or switch its stereopreference to Prelog. Moreover, the knowledge obtained from LfSDR1 could be further transferred to the five other SDRs (four mined SDRs and one reported SDR) that have 21−48% sequence identities with LfSDR1. The stereopreferences of these SDRs were able to be switched either from anti-Prelog to Prelog or from Prelog to anti-Prelog by mutagenesis at related positions. In addition, further optimization of LfSDR1 can access stereocomplementary reduction of several halogen-substituted acetophenones with high stereoselectivity (up to >99%), resulting in some valuable chiral alcohols for the synthesis of pharmaceutical agents.

No abstract

No abstract

8‐Oxoguanine DNA glycosylase1 (OGG1)‐initiated base excision repair (BER) is the primary pathway to remove the pre‐mutagenic 8‐oxo‐7,8‐dihydroguanine (8‐oxoG) from DNA. Recent studies documented 8‐oxoG serves as an epigenetic‐like mark and OGG1 modulates gene expression in oxidatively stressed cells. For this new role of OGG1, two distinct mechanisms have been proposed: one is coupled to base excision, while the other only requires substrate binding of OGG1––both resulting in conformational adjustment in the adjacent DNA sequences providing access for transcription factors to their cis‐elements. The present study aimed to examine if BER activity of OGG1 is required for pro‐inflammatory gene expression. To this end, Ogg1/OGG1 knockout/depleted cells were transfected with constructs expressing wild‐type (wt) and repair‐deficient mutants of OGG1. OGG1's promoter enrichment, oxidative state, and gene expression were examined. Results showed that TNFα exposure increased levels of oxidatively modified cysteine(s) of wt OGG1 without impairing its association with promoter and facilitated gene expression. The excision deficient K249Q mutant was even a more potent activator of gene expression; whereas, mutant OGG1 with impaired substrate recognition/binding was not. These data suggested the interaction of OGG1 with its substrate at regulatory regions followed by conformational adjustment in the adjacent DNA is the primary mode to modulate inflammatory gene expression.

No abstract