Evidence for cell wall recycling cyanobacteria: characterization of NagZ

Our efforts to characterize β-1,4-N-acetylglucosanimindase, also known as NagZ, in the cyanobacterium Nostoc punctiforme have revealed several unique phenotypes and reaffirmed previously established mechanisms. Enzyme assays show that nagZ hydrolyzes the β-1,4 glycosidic bond between NAM and NAG, as previously reported in E. coli and that nagZ mutants lose this hydrolytic ability. This defect is repaired by the construction of a nagZ complementation strain and enhanced by the construction of an overexpression strain. These mutants also show sensitivity to certain environmental stressors such as lysozyme, EDTA, bile salts and reduced light conditions. Interestingly, nagZ mutants are also more susceptible to β-Lactam antibiotics but do not display signs of β-Lactamase induction. GFP localization shows that NagZ is a cytoplasmic protein that's been conserved in the Glycoside Hydrolase Family 3 enzymes.