Chemistry Reference
In-Depth Information
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Much of the information about the catabolism of PG has been derived from the study of
mucopolysaccharidoses
(Type I-VII, see below). These inborn human genetic disorders are
characterized by lysosomal accumulation in tissues and excretion in urine of oligosaccharides
derived from incomplete degradation of GAGs due to defi ciency of one or more lysosomal
hydrolases. Clinical manifestations vary from mild symptoms up to severe cases resulting in
early death. The disorders are amenable by prenatal diagnosis; the incidence is 1/30 000
births. Another group of lysosomal storage diseases with similar symptoms, the
sphingolipi-
doses
, comprises disorders characterized by single sphingolipid accumulation in bone marrow,
liver, brain and other cells. Defi ciencies of galactosidase, glucosidase and hexosaminidases
cause the storage of incompletely degraded glycocerebrosides and gangliosides within the
lysosomes (please see also Figure 10.5 and Table 30.1 ).
Type
Name
Impaired
degradation of
Symptoms
Enzyme defi ciency
I
Hurler disease (IH)
Scheie disease (IS)
DS, HS
Dwarfi sm, gar-
goyle face, mental
retardation, cornea
cloudiness
α
- Iduronidase
II
Hunter disease
DS, HS
As in type I but
less severe
Iduronide 2 - sulfate sulfatase
III
Sanfi lippo disease
(polydystrophic
oligophrenia)
Type A, Type B,
Type C, Type D
HS
Severe mental
retardation, low
physical altera-
tions
(A) HS sulfamate sulfatase
(B)
- N - Acetyl - glucosaminidase
(C) Acetyl - CoA
α
- glucosamide
N - acetyl - transferase
(D) HS N - Acetylglucosamine
6 - sulfate sulfatase
α
IV
Moquio - Brailsford
disease (osteochondo-
dystrophy)
KS, CS
6 - sulfate
Dwarfi sm, skeletal
deformities, cornea
cloudiness
(A) N - Acetyl - galactosamine
6 - sulfate sulfatase
(B)
β
- Galactosidase
VI
Marotaux - Lamy
disease
DS, CS
4 - sulfate
Skeletal deformi-
ties, cornea cloudi-
ness, normal
mental develop-
ment
N - Acetylgalactosamine 4 - sulfate
sulfatase
VII
β
- Glucuronidase
defi ciency
CS, DS, HS
As in type I but
variable symptoms
β
- Glucuronidase
