Sphingolipids Flashcards
Found in the outer leaflet of the cell membrane form part of the glycocalyx of the cell surface
Glycosphingolipids
Functions of sphingolipids
In intercellular communication and contact
As receptors for bacterial toxins
As ABO blood group substances
Are lysosomal storage diseases with defects in the catabolic pathway for sphingolipids
Sphingolipidoses
Principal structural lipid of the membranes of nervous tissue
Backbone: sphingosine (amino acohol) not glycerol
4C
Sphingomyelin
Fatty acids present in the sphingomyelin of myelin sheath
Lignoceric acid
Nervonic acid
Fatty acid present in the sphingomyelin of gray matter
Stearic acid
Sphingomyelin is converted to
Ceramide and choline
via sphingomyelinase
Ceramide + Choline is converted to
Sphingosine and fatty acid
via ceramidase
Due to deficiency of sphingomyelinase
Mental retardation
Ataxia
Seizure
Macular degeneration and cherry red spot
Niemann-Pick Sphingomyelinase Disease
Due to deficiency of ceramidase
Farber’s Ceramidase disease
Due to deficiency of beta glucosidase
Three forms
Gaucher’s Beta Glucosidase Disease
Marked hepatosplenomegaly
Severe neurologic progression to death
Infantile 1-2 months
Milder neurologic involvement
Juvenile 2-6 years
Non-neuropathic form
Adult
Also called globoid leukodystrophy
Due to deficiency of beta galactosidase
Galactosylceramide accumulates in the white matter
Infantile disease 2-6 months
Mental retardation
Leukodystrophy
Optic atrophy
Presence of globoid cells in the brain
Krabbe’s disease
Sulfogalactocerebroside
Sulfuric acid ester of galactosylceramide
Major sulfolipid of the brain
Accounts for 15% of the lipids of the white matter
Sulfatide
Due to deficiency of arylsulfatase A
Mental retardation Leukodystrophy Optic atrophy Psychosis Dementia
Metachromatic leukodystrophy
Ceramide oligosaccharides
Sugars present are usually glucose, galactose or N-acetylgalactosamine
Globoside
Example of globoside
Lactosylceramide component of erythrocyte membrane
Ceramide trihexosidase - abundant in the kidney
Due to deficiency of alpha-galactosidase
Ceramide trihexoside accumulates in the kidney progessing to renal failure
Other/s: skin rash, pains in lower extremities
Fabry’s disease
Contain sialic acid or N-acetylneuraminic acid
Highly concentrated in the ganglion cells of the CNS particularly in nerve endings
CNS is unique because more than half of sialic acid is in ceramide-lipid bound form
Gangliosides
Due to deficiency of a beta-galactosidase
GM1 accumulates in the brain and other organs
Mental retardation Seizures Blindness Impaired psychomotor function Hepatosplenomegaly Cherry red spot in 50% of infantile form
Generalized gangliosidosis
Due to deficiency of hexosaminidase A
GM2 accumulates in the brain
Forms
infantile (3-6 months)
juvenile
adult
Mental retardation
Seizures
Blindness
Cherry red spot on macula
Tay Sach’s disease
