β-N-Acetylglucosaminidase from Streptococcus pneumoniae
β-N-Acetylglucosaminidase (NAG) is a lysosomal enzyme that is expressed in various tissues, including kidney, liver and lungs. NAG can cleave N-acetyl-glucosamine, a monosaccharide derivative of glucose. Its concentration in urine is minimal due to its inability to cross the glomerular basal membrane. Increased concentration of NAG in urine indicates renal tubular cell breakdown. Acute Kidney Injury (AKI) is the sudden loss of kidney functions, causing electrolyte imbalance, and retention of urea and other nitrogenous products. NAG has become one of the most studied and used biomarkers for the detection and diagnosis of AKI.
This enzyme, sometimes called β-N-acetylhexosaminidase, is reported to liberate terminal β-linked N-acetylglucosamine and N-acetylgalactosamine from a variety of substrates. One unit will hydrolyze 1.0 μmole of p-nitrophenyl N-acetyl-β-D-glucosaminide to p-nitrophenol and N-acetyl-D-glucosamine per min at the pH 5 at 37 °C.