Neuraminidase activity in middle ear effusions.
Analyses of Streptococcus pneumoniae culture filtrates and middle ear effusions (MEE) containing S pneumoniae for various hydrolytic enzymes have demonstrated substantial levels of neuraminidase activity when measured employing a sensitive fluorometric assay. S pneumoniae neuraminidase exhibits optimum activity near neutral pH (6.0 to 6.5), and catalyzes the cleavage of sialic acid residues from glycoproteins, gangliosides and mucopolysaccharides. S pneumoniae begins secreting large amounts of neutral neuraminidase (mean [means] = 43.3 units/mL culture filtrate) when cells enter the stationary phase. Nearly all (96%) human chronic MEEs yielding positive cultures for S pneumoniae contain neuraminidase activity (means = 0.200 units/mg protein), while only 21.1% to 45.5% of all other effusions contain the enzyme. Middle ear effusions obtained from S pneumoniae infected-chinchillas contained large amounts of neuraminidase activity (approximately 200 units/mL), which decayed exponentially in vivo with an apparent half-life of 8 1/2 days. Three neuraminidase isoenzymes (designated I-III) were identified in S pneumoniae culture filtrates, as well as in MEEs from chinchillas infected with the organism, using a combination of ion-exchange and gel filtration chromatography. With 4-methylumbelliferyl-N-acetylneuraminic acid serving as substrate, preparation I from both culture filtrates and MEEs was characterized by a high Michaelis constant (Km), while forms II and III had low Km values. Preferred substrates were orosomucoid and neuramin-lactose; gangliosides, thyroglobulin, and bovine submaxillary mucin were poorer substrates.
D000818:Animals; D001419:Bacteria / Q000472:pathogenicity; D001424:Bacterial Infections / Q000201:enzymology*; D002648:Child; D002675:Child, Preschool; D002682:Chinchilla; D002908:Chronic Disease; D003470:Culture Media; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007223:Infant; D008297:Male; D009439:Neuraminidase / Q000096:biosynthesis / Q000378:metabolism*; D010033:Otitis Media / Q000201:enzymology*; D010034:Otitis Media with Effusion / Q000201:enzymology*
D003470:Culture Media; D009439:Neuraminidase