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THE ACTIVITY OF GANGLIOSIDE SIALIDASE IN THE DEVELOPING HUMAN BRAIN

—The development of ganglioside sialidase and of four different p‐nitrophenyl glycosidases in human brain was investigated including both prenatal and postnatal periods. The developmental curve for sialidase was different from that of the other glycosidases. While p‐nitrophenyl glycosidases showed high activities at an early stage of development (21 foetal weeks), and remained at about the same level, ganglioside sialidase was not detected before the foetal age of 15‐20 weeks. The sialidase activity at term reached about half the adult level and there was a possible decrease in activity during the first year. The sialidase activity then increased, approaching the adult level at about the age of 5 years. The development of the ganglioside sialidase activity in human brain can be related to changes in the concentration of individual brain ganglioside components. The late maturation of the sialidase system in relation to other glycohydrolases is also discussed as a possible protective mechanism for sialic acid‐containing compounds during the early period of development.