Molecular Properties and Differentiation of Acetylcholinesterase in Sea Urchin Embryos*

Abstract

The two molecular forms of acethylcholinesterase (EC 3.1.1.7) in sea urchin embryos were characterized by several physical methods. The sedimentation coefficients determined by sucrose gradient centrifugation are 7.6s and 10.6s. The Stokes radii determined by gel filtration are 65 a and 9 1 8. From these parameters, molecular weights were estimated as 190,000 and 380,000; the one is twice as large as the other. Both forms have similar electric property and buoyant density in a CsCl gradient. When the enzyme solution was concentrated, the 10.6s form became predominant. These results suggest that the two forms are monomer and dimer. The sea urchin enzymes resemble globular forms of acetylcholinesterase of the electric organ of fishes.The activity of the enzyme abruptly increases in post-gastrulation embryos. Inhibition of concomitant protein synthesis by a specific inhibitor, emetine, does not affect the increase in enzyme activity. The result suggests that post-translational processes may be involved in the differentiation of this enzyme in sea urchin development.The following sea urchins were used in the study: Strongylocentrotus purpuratus, Strongylocentrotus frunciscanus, and Dendruster excentricus.A marked increase in acetylcholinesterase activity occurs in post-gastrulation embryos o f the sea urchin (5, 39). Concomitantly, enzymes sensitive to an inhibitor of cholinesterase appear among the esterases resolved by polyacrylamide gel electrophoresis (37,38,40) and by immunoelectrophoresis (49). The enzyme activity is first localized in the mesenchyme cells of the young pluteus larva (39). The great increase in activity at a defined stage in development and its concentration in a specific region of the embryo make this system a useful model for the study of temporal and spatial controls of differentiation in early embryogenesis.Acetylcholinesterase of post-gastrulation sea urchin embryos exists in two forms in the supernatant fraction of the homogenate. The same two forms are present in the preparation of enzyme solubilized from the particulate fraction. Approximately 60% of the enzyme activity is associated with the particulate fraction. These two molecular forms have a similar electric property but differ in molecular size (39).In the present study, the two molecular forms were characterized further by several physical methods. The results show that the two forms are monomer and dimer, and that they resemble globular forms of acetylcholinesterase obtained from the electric organ of fishes (30). The present study, furthermore, demonstrates that ontogenetic changes in enzyme activity is not immediately dependent upon protein synthesis.

cDNA cloning, in vitro expression, and biochemical characterization of cholinesterase 1 and cholinesterase 2 from amphioxus

“…The agnathan vertebrates Myxine glutinosa [10] and Petromyzon marinus [11,51] possess only a single ChE, AChE, in both globular (both G 2 and G 4 ) and asymmetric forms. The AChE activity of larval urochordates and echinoderms is found as both G 2 and G 4 [52,53]. These data suggest that alternative splicing of the H and T exons of ChE genes is already present in deuterostome invertebrates, the invertebrate lineage that gave rise to the chordates.…”

Developmental abnormalities and neurotoxicological effects of CuO NPs on the black sea urchin Arbacia lixula by embryotoxicity assay

“…AChE plays a key role during the migration of PMCs and spicule elongation (Ohta et al, 2009). Indeed, AChE activity is necessary for the development of several M. Maisano et al / Marine Environmental Research xxx (2015) 1e7 5 species of sea urchins including Paracentrotus depressus (Ozaki, 1974), Strongylocentrotus purpuratus (Ozaki, 1976), Hemicentrotus pulcherrimus (Akasaka et al, 1986). In embryos, AChE level increases during gastrulation and post-gastrulation, as it is probably involved in the neuronal differentiation (Akasaka et al, 1986;Ohta et al, 2009).…”

Histochemical localization of cholinesterase activity in the dental epithelium of guinea pig teeth

“…However, Tsuzuki and Kitamura (1987) reported a localization of ChE in the ecto-mesenchymal cells of the developing mandibular process (stage 20-Christie's nomenclature) of rats and its gradual disappearance at and around the stage of entry of the mandibular nerve (stage 22-Christie's nomenclature). On the other hand, some molecular forms of ChE are reported to be soluble and highly unstable during fixation and tissue processing (Ozaki 1974(Ozaki , 1976. For instance, histochemical detection of AChE in the human intact erythrocyte membrane is difficult unless special fixative procedures are used.…”