[Heat stability of cholinesterase and non-specific esterases during development of hybrids of the sea urchins Stongylocentrotus droebachiensis and S. intermedius].

Acetylcholine esterase (AchE) and non-specific esterases were studied during the development of sea urchins Strongylocentrotus droebachiensis and S. intermedius and their hybrids by means of electrophoresis and measurements of enzyme thermostability. Two AchE fractions were found which differed by thermostability. At the late gastrula stage, the therolabile form predominated and at the mid-pluteus stage the thermostable one. Non-specific esterases in both the species of sea urchins are represented by complex isozyme systems. Their changes during development are accompanied by the changes in thermostability and electrophoretic patterns. The thermostability of esterases at the pluteus stage in the hybrids is higher than in the maternal species, apparently, due to the appearance of the thermostable enzyme which appears in the paternal species provisionally at the prism stage.