Beschreibung:
<jats:p>
Conditions optimum for the assay of alkaline phosphatase of marine pseudomonad B-16 (ATCC 19855) and for maintaining the activity of the enzyme have been determined. The pH for optimal activity of the cell-bound enzyme was 9.0, whereas that for the enzyme after its release from the cells exceeded 9.4. Release was effected by first washing the cells in 0.5 M NaCl and then suspending them in 0.5 M sucrose. In the absence of salts, the activity of the cell-bound enzyme decreased rapidly at 25 C and less rapidly at 4 C. This loss of activity could be arrested but not restored by adding Mg
<jats:sup>2+</jats:sup>
. In the presence of Na
<jats:sup>+</jats:sup>
, activity of the cell-bound enzyme dropped to about 50% of that prevailing initially, but in this case adding Mg
<jats:sup>2+</jats:sup>
restored enzyme activity completely. The activity of the enzyme after its release from the cells into 0.5 M sucrose was approximately 50% of that of the equivalent amount of enzyme in the original cells. This activity was relatively stable at both 25 and 4 C. Adding Mg
<jats:sup>2+</jats:sup>
to the released enzyme restored its activity to that of the cell-bound form. The synthesis of alkaline phosphatase by the cells was not affected by adding 50 mM inorganic phosphate to the growth medium. The
<jats:italic>
K
<jats:sub>m</jats:sub>
</jats:italic>
of the released enzyme for
<jats:italic>p</jats:italic>
-nitrophenyl phosphate was found to be 6.1 × 10
<jats:sup>−5</jats:sup>
M.
</jats:p>