Properties of an inducible extracellular neuraminidase from an Arthrobacter isolate

Abstract

Th4 elective isolation of a soil microorganism, tentatively assigned to the genus Arthrobacter, which produced an extracellular neuraminidase is described. The secretion of neuraminidase from washed cells in minimal medium required the presence of sialo-containing glycoproteins, whereas free N-acetylneuraminic acid or N-acetylmannosamine were poor inducers. No enzyme could be detected in the induction filtrate of cells, in the absence of inducer or in the culture filtrate of cells grown in a complete medium. The routine enzyme inducer was a hot-water extract of 'edible bird's nest'. Mild acid treatment (0.05 N H2SO4) of this extract increased enzyme activity two- to threefold and the specific activity about eightfold. Neuraminidase induction with acid-treated bird's nest was manifested at a linear rate for 6 h without increase in cell number. No other anticipated glycohydrolase or protease activities were found. The amount of enzyme located within the cells was barely detectable as compared to that found in the induction filtrate. Experiments with chloramphenicol or chlortetracycline indicate that de novo protein synthesis was required for neuraminidase production and that this exoenzyme was not released from a preformed pool. Neuraminidase from this source has an apparent molecular weight of 87,000, a pH optimum of 5 to 6, and an apparent K(m) of 2.08 mg/ml for collocalia mucoid and 3.3 x 10-3M for N-acetylneuraminlactose and is insensitive both to Ca2+ ions and ethylenediaminetetraacetic acid. Preliminary studies indicate that the enzyme can hydrolyze α-2,3-, α 2,6-, or α-2-8-N-acetylneuraminylglycosidic linkages. From total activity data and purification criteria, it would appear that this isolate can produce about 5 mg of enzyme per liter of induction medium.