Molecular forms of acetylcholinesterase in the developing chick visual system.
The developmental profiles of the enzyme acetylcholinesterase, and of some of its quaternary structural forms, characterized by discrete sedimentation coefficients, have been comparatively analyzed in chick retina and optic tectum, between embryonic day 8 and day 10 after hatching. Four molecular species of AChE have been characterized in both retina and tectum during this developmental period: two of them with sedimentation coefficients of 11S and 6S, accounting together for 94-99% of the AChE activity in the initial homogenate, can be easily extracted by homogenization in a buffer containing 1% Triton X-100 and 1 M NaC1, at 4 degrees C. The other two, however, are not extractable by such treatment, but can be released by collagenase from the residue left after the detergent-salt extraction; they have apparent sedimentation coefficients of 21.5S and 16.5S and represent, together, less than 2% of activity in the initial homogenate. All four forms of the enzyme show distinctive patterns of change during the developmental period considered, with significant differences between retina and tectum. These differences are discussed in the context of the specific roles of retina and tectum in the visual process.