The extracellular nuclease activity of Micrococcus sodonensis: IV. Physical studies, characterization as a glycoprotein and involvement with the cell wall

Abstract

1. 1. The molecular weight and s 20,w of Micrococcus sodonensis nuclease were found to be concentration dependent and extrapolation to zero concentration yielded values of 500 000 and 2.2 S, respectively. The concentration dependence and behaviour of the peak in sedimentation velocity experiments are indicative of an asymmetric molecule. 2. 2. The enzyme was shown to be a glycoprotein consisting of 21% carbohydrate covalently linked to the protein moiety. Glucosamine, glucose, galactose and rhamnose were identified as the component sugars and were present in a ratio of 4:2:1:1. A serine-glucosamine linkage involving at least 80% of the serine residues was demonstrated. 3. 3. Amino acid analyses showed the enzyme to be low in cysteic acid residue and to contain relatively high amounts of serine, threonine, glycine and proline. Unexpected high values for tryptophan were shown to be a result of the presence of amino sugar. 4. 4. The carbohydrate moiety of purified enzyme was shown to be related both chemically and immunologically to the cell wall carbohydrate and active enzyme was found bound in a stable configuration to the cell wall. 5. 5. The possible role of the wall in enzyme formation is discussed.