The prokaryotic adaptive immune system is greatly influenced by the effector protein Cas9, which is connected with the CRISPR system and targets foreign DNA.

Despite extensive research and repurposing for uses such as genome editing, Streptococcus pyogenes CRISPR-genesis Cas9's and evolution remain poorly known.

In this study, we look at the evolution of Cas9 from revived ancient nucleases (anCas) in extinct firmicutes species, the last of which last existed 2.6 billion years ago.

We show that in comparison to contemporary Cas9 enzymes, these prehistoric variants were far more adaptable in terms of their guide RNA and protospacer-adjacent motif requirements.

Furthermore, anCas demonstrates significant levels of activity with both single-stranded DNA and single-stranded RNA, demonstrating a steady palaeoenzymatic transition from nickase

In human cells, RNA can target and perform editing activities. A functionally flexible evolutionary pathway that led to ancient enzymes is shown through the prediction and characterization