Advances in menaquinone biosynthesis: sublocalisation and allosteric regulation

•Menaquinones (MKs) are involved in bacterial electron transport and adaptation.•The Men pathway is the most predominant of two bacterial pathways to make MKs.•Men enzymes are of interest as drug targets and in bioengineering applications.•There are still gaps in our understanding of the more diverse Men enzymes.•Their important roles/toxicity mean MKs levels in a cell need tight regulation.•Recent work shows regulation via feedback inhibition and sublocalisation. Menaquinones (vitamin K2) are a family of redox-active small molecules with critical functions across all domains of life, including energy generation in bacteria and bone health in humans. The enzymes involved in menaquinone biosynthesis also have bioengineering applications and are potential antimicrobial drug targets. New insights into the essential roles of menaquinones, and their potential to cause redox-related toxicity, have highlighted the need for this pathway to be tightly controlled. Here, we provide an overview of our current understanding of the classical menaquinone biosynthesis pathway in bacteria. We also review recent discoveries on protein-level allostery and sublocalisation of membrane-bound enzymes that have provided insight into the regulation of flux through this biosynthetic pathway.