Recombinant DNA Topoisomerases for Biomedical Research and Pharmaceutical Discovery: Expression Platforms, Functional Assays, and Translational Applications

DNA topoisomerases regulate DNA topology during replication, transcription, recombination, and chromosome segregation, and several are established targets of anticancer and antibacterial drugs. Recombinant production of these enzymes underpins biochemical screening, structural biology, and mechanistic pharmacology. This narrative review summarizes topoisomerase classification and catalytic mechanisms, recombinant expression platforms in bacteria, yeast, and human cells, purification and quality-control criteria, functional and counter-screening assays, and translational applications, including isoform-selective TOP2B inhibition. Quantitative statements are limited to values traceable to primary sources; studies using different scales, constructs, or units are reported separately rather than ranked. The evidence indicates that expression yield alone does not establish platform suitability: enzymatic activity, isoform identity, and assay controls must also be demonstrated. Isoform-selective catalytic inhibition, exemplified by the preclinical TOP2B inhibitor topobexin, illustrates the potential of recombinant human enzymes in drug discovery, although these findings remain experimental.