Alkaline phosphatase of sea urchin embryos: Chromatographic and electrophoretic characterization.

A change in the molecular form of alkaline phosphatase in sea urchin embryos accompanies the marked increase in activity that occurs at gastrulation. On the basis of chromatographic and electrophoretic analyses, two major classes of alkaline phosphatase are identified: early enzyme, from unfertilized eggs to mesenchyme blastula, characterized by a major peak of activity, with a K_av of 0.123 on Sephadex G-200 columns, elution from DEAE-Sephadex columns by 0.5 M NaCl, and a migration value of 0.51 (relative to bromophenol blue) after electrophoresis in 7.5% polyacrylamide gels; late enzyme, from gastrula to plutei, characterized by a K_av of 0.137, elution from DEAE-Sephadex by 0.55–0.75 M NaCl, and a migration value of 0.56. By chromatographic and electrophoretic criteria the early enzyme appears to have a slightly greater molecular volume, lower net negative charge, and more heterogeneous composition than the late enzyme. Both enzyme preparations were maximally active at a pH 9.4–9.5. Enzyme from all stages appears to be predominantly associated with cell membranes. Extracting the enzyme by treatment with n-butanol, precipitating the enzyme from the dialyzed aqueous phase with ethyl alcohol, and chromatographing the alcohol preparation on columns of sieving and anion-exchanging media resulted in a substantial purification of the enzyme from all stages.