Related to Defective Sialic Acid Transport

DISEASES RELATED TO DEFECTIVE SIALIC ACID TRANSPORT 

When sialic acid-containing compounds are degraded, the liberated sialic acid cannot be further metabolized within the lysosome and must be transported out of the lysosome. A complex metabolic machinery appears to operate for this process, involving a transport protein specific for sialic acid. Free sialic acid is then metabolized by a cytoplasmic enzyme, V-acetylneuraminate lyase. If one of the essential components in this transport system is defective, free sialic acid cannot be removed from the lysosome and consequently accumulates abnormally since it cannot be metabolized intralysosomally. Since 1979, the unique genetic disorder Salla has been known in a delimited region of Finland. The disease is caused by defective transport of free sialic acid out of the lysosome (see appropriate section in Scriver et a/., 1995). 

Molecular Genetics. The putative sialic acid transporter protein has not been isolated. Thus, no information is available regarding the molecular genetic aspects of Salla disease and its infantile variant. 

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