Implication of membrane bound neuraminidase in developmental and adaptational processes of different vertebrate species.
Determination of brain membrane-bound sialidases by means of 4-methylumbelliferyl-neuraminic acid as exogenous, artificial substrate provides a good measure for functional implications of this enzyme in brain ontogeny and adaptation to changes in different environmental parameters. In rainbow trout and Cichlid fish a striking increase in brain sialidase-activity occurs during ontogenetical development, especially in post-hatching-larvae up to free swimming, reaching adult values of 75 and 50 nmol of sialic acid released per h and mg protein, respectively. Dark adapted Cichlid fish show a considerably lower turnover in brain (28 nmol per h and mg protein). Principally sialidase activity is in mammals about 5-fold lower than in fish and seems to be highest in cortex (compared with cerebellum and basal brain). Hibernating dwarf- and golden hamsters show a significant lower sialidase activity in summer, though these differences also occur in non-hibernating animals kept at constant ambient temperatures, thus indicating a temperature-independent, possibly genetically fixed enzyme regulation.
Seybold
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Zoological Institute, University of Stuttgart-Hohenheim, D-7000 Stuttgart 70 (Hohenheim), F.R.G.
Swoboda
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Rahmann
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