This work presents a method for purification of lysostaphin, a glycylglycine endopeptidase, from the culture liquid of S. simulans biovar staphylolyticus to homogeneity in a few steps. The method includes ultrafiltration and ion-exchange and hydrophobic chromatographies. The enzyme was isolated in preparative amounts with the yield of 51%. Some physical and chemical properties of the enzyme are described.
The rate of lysostaphin-catalyzed lysis of staphylococci follows the Michaelis-Menten equation at [E](0) << [S](0), i.e., the activity of the enzyme is proportional to its concentration. This equation is proposed for determining the specific activity of lysostaphin. The apparent activation energy of hydrolysis of pentaglycine bridges in Staphylococcus peptidoglycan is 77.9 kJ/mol.
A sensitive and precise method for quantifying protease and peptidase activities is suggested. N-Terminal amino groups of peptides which are formed during hydrolysis of the substrates react with trinitrobenzenesulfonic acid (TNBS), and the trinitrophenyl (TNP) derivatives are determined spectrophotometrically. Spontaneous hydrolysis of TNBS is considerably diminished on trinitrophenylation at pH 7.4 rather than at pH 9-10 as is usually used. The trinitrophenylation method can be used to determine the initial rate of hydrolysis and the kinetics of reactions catalyzed by proteases and peptidases.
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