MOLECULAR PROPERTIES AND DIFFERENTIATION OF ACETYLCHOLINESTERASE IN SEA URCHIN EMBRYOS*

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Abstract
The 2 molecular forms of acetylcholinesterase (EC 3.1.1.7) in sea urchin embryos were characterized by several physical methods. The sedimentation coefficients determined by sucrose gradient centrifugation were 7.6S and 10.6S. The Stokes radii determined by gel filtration were 65 .ANG. and 91 .ANG.. From these parameters MW were estimated as 190,000 and 380,000. Both forms had similar electrical properties and buoyant density in a CsCl gradient. When the enzyme solution was concentrated, the 10.6S form became predominant. The 2 forms were probably monomer and dimer. The sea urchin enzymes resembled globular forms of acetylcholinesterase of the electric organ of fishes. The activity of the enzyme abruptly increased in post-gastrulation embryos. Inhibition of concomitant protein synthesis by a specific inhibitor, emetine, did not affect increase in enzyme activity. Post-translational processes may be involved in the differentiation of this enzyme in sea urchin development. The sea urchins used were Strongylocentrotus purpuratus, S. franciscanus, and Dendraster excentricus.