Looks can be deceiving: Bacterial enzymes work through unanticipated mechanism.

It was not until the ingenious works of Anton van Leeuwenhoek in the 17th century that bacteria were first discovered and understood to be a “new” form of life on Earth (1). For the next 200 y, bacteria were largely ignored and thought to simply be “bags of proteins,” even though it was recognized that they could have enormous impacts on human health. It is now widely appreciated that bacteria are incredibly complex organisms that can function in a manner that mimics a multicellular organism (2, 3). The ability of bacterial cells to constantly produce and remodel their cell wall is no exception to this, and myriad crucial findings about this process have been made over the last century. One of the most seminal of these discoveries came in the 1940s when β-lactam−containing molecules were found to combat bacterial infections. More recently, the targets of these drugs, the penicillin-binding proteins, as well as other protein machinery have been identified as essential elements for construction of the complex mesh that keeps these cells intact, the peptidoglycan (PG). Still, many mysteries remain about exactly how bacterial cells grow and divide. In particular, while enzymes that cleave and tailor portions of the PG are known to play important roles in microbial survival, they are dramatically understudied. Taguchi et al. (4) shed light on two enzymes in Streptococcus pneumoniae , MpgA and MpgB, shown to cleave a nascent carbohydrate strand to liberate newly synthesized PG. While previous studies postulated that this occurred in a fashion similar to that utilized by a close relative, the lytic glycosylase MltG in Escherichia coli [1,6-anhydroMurNac product (5)], Taguchi et al. instead discover that MpgA and MpgB act as muramidases [saccharide product with reducing end (6)]. Amazingly, they determined that a single amino acid is largely responsible for … [↵][1]1To whom correspondence may be addressed. Email: carlsone{at}umn.edu. [1]: #xref-corresp-1-1