Studies of Mammalian Sialidases

Sialidase in chickens has been found to be fully active at birth, whereas in mammalian organs, sialidase activity is found to increase over a period of time after birth until adult levels are reached. This probably reflects the relative stages of development at birth for different species. 

Several studies have reported on sialidase activity in developing rat brains. Carubelli (1968) found that sialidase, active toward sialyllactose and present in the 100,000g supernatant, increased in a linear fashion from the low level found during the first week of life and reached the specific activity found in the mature animal by the end of the third week of life. These observations were confirmed by Quarles and Brady (1970) and by Roukema et al. (1970), who also showed that the sialidase activity remained essentially constant for 150 days. Carubelli and Tulsiani (1971) found that soluble sialidase activity in rat liver is low in fetal liver, undergoes a sharp increase during 3 to 4 days prior to birth, and is essentially fully active at birth. In contrast, the particulate enzyme is fully active during the last week of prenatal development. In this work, they also studied the particulate sialidase in brain. In contrast to Carubelli s (1968) earlier finding for the soluble sialidase (which they repeated), they found that the particulate sialidase had full activity a week before birth. 

Ohman and Svennerholm (1971) measured the appearance of sialidase activity toward ganglioside substrate in developing human brain. Activity was first detected in the fetal brain at 15 to 20 weeks and by term had increased to half of the adult level. During the first year of life sialidase activity may decrease slightly, and then it increases until it approaches the adult level at 5 years. The appearance of sialidase activity in the later stages of development may reflect the need for the enzyme to alter, or to help in degradation of, the more complex sialyl compounds synthesized, and these latter in turn may serve to induce sialidase activity. 

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