456
DEGRADATION
[47]
of enzymes in cultured cells and serum are used in other laboratories. 44'4~ Deficiency of a-L-iduronidase, fl-galactosidase, or fl-hexosaminidase in cultured amniotic fluid cells may be used for the prenatal diagnosis of mucolipidosis II; the level of fl-hexosaminidase in the amniotic fluid is elevated. 46 44 J. H. Glaser, W. H. McAlister, and W. S. Sly, J. Pediatr. 85, 192 (1974), 4~ G. H. Thomas, H. A. Taylor, L. W. Reynolds, and C. S. Miller, Pediatr. Res. 7, 751 (1973). 46 p. Aula, J. Rapola, S. Autio, K. Raivio, and O. Karjalainen, J. Pediatr. 87,221 (1975).
[47] E n z y m i c D i a g n o s i s o f S p h i n g o l i p i d o s e s By
KUNIHIKO SUZUKI
The sphingolipidoses are defined as disorders of sphingolipid metabolism caused by genetic mutations of the hydrolytic enzymes which normally catabolize these sphingosine-containing lipids. Under this definition, two disorders are included for consideration in this section, although they do not involve metabolism of glycolipids. They are Niemann-Pick disease (sphingomyelinase deficiency) and Farber's lipogranulomatosis (ceramidase deficiency). On the other hand, the recently reported disease of ganglioside synthesis ~is not included under the above definition. The underlying genetic enzymic defects of the sphingolipidoses have now been largely clarified. Affected patients can be diagnosed definitively by appropriate enzyme assays, and heterozygous carriers of these diseases can be identified with reasonable reliability. In addition, in the majority of the sphingolipidoses, affected fetuses have been diagnosed during pregnancy by enzymic assays on cultured amniotic fluid cells. This section provides descriptions of reliable and practical procedures for enzymic diagnosis of the sphingolipidoses. For clinical, pathological, and analytical details of the individual diseases, the appropriate chapters in the book edited by Stanbury et al. 2 are suggested. A book that has a similar purpose as this section has also been published recently2 P. H. Fishman, S. R. Max, J. F. Tallman, R. O. Brady, N. K. Maclaren, and M. Corblath, Science 187, 68 (1975). 2 j. B. Stanbury, J. B. Wyngaarden, and D. S. Fredrickson (eds.), "The Metabolic Basis of Inherited Disease," 4th ed. McGraw-Hill, New York, 1978. a R. H. Glew and S. P. Peters (eds.), "Practical Enzymology of the Sphingolipidoses." Alan R. Liss, New York, in press.
[47]
457
E N Z Y M I C D I A G N O S I S OF S P H I N G O L I P I D O S E S
POLYSIALOGANGLIOSIDES
1
Ceramide - Glc - C~I- Gal- GalNAc
Ce ramide -GIc -Gal ~C.alNAc - Gal -~- ..... Ce ramide -Glc -C.el-(~tlNAc - Gel (GM])
Ceramide-Glc- Gal- Gal
Ceramide - GIc - Gal- C~INAc -9- . . . . . . . Ce ramide - GIe -Gal- GalNAc
-GIc-Gal ~
Ceramide -phospho rylchoUne
Cer!mideGlc
(Sphingomyelin)
(GI....... broside)
(~
" ~
~ ~_.._
Ceramide- GIc-Gal- NeuAc
c ~-~
(GM2)
(GM3)
ide- GRI- Gal
/
Ceramide-Gal ~ C e r a m i d e - C ~ l . S 0 4 (~
(C,~,act..... broside)
(~
(Sulfatide)
Sphlngosine
Flo. I. Chemical and metabolic relationship among major sphingolipids, and the locations of the genetic blocks. The numbers correspond to those in Tables I and II.
Diseases and Enzymic Defect The sphingolipids involved in the genetic sphingolipidoses can be systematically depicted in simplified notations as an interrelated series of compounds (Fig. 1). A specific genetic disease is known for every degradative step in Fig. 1, caused by the deficiency of the hydrolase that normally catalyzes that particular step, except for the steps involving desialylation of gangliosides (neuraminidase) and degradation of lactosylceramide (/3-galactosidase). These disorders are tabulated in Table I together with their clinicopathological characteristics, analytical abnormalities, and the affected enzymes. Enzyme Sources for Diagnostic Assays A variety of tissue sources can be utilized for the enzymic assays for diagnosis of the sphingolipidoses. Each source has its advantages and disadvantages. Solid tissues, such as brain, liver, spleen, or kidney, are generally excellent enzyme sources in cases in which antemortem diagnosis was not established. Almost all enzymes involved in the sphingolipidoses are sufficiently stable to allow reliable assays even with organs obtained 12 hr or longer after death. However, in view of other readily available specimens, solid tissue biopsies should no longer be permitted for the purpose of antemortem diagnosis of the sphingolipidoses. Serum is easily obtained and is a reliable source for some of the enzymes. However, the enzymic activities in serum are generally lower than those in cellular sources, and some of the enzymes cannot be assayed reliably in serum. Furthermore, some serum hydrolases appear to be less
458
[47]
DEGRADATION
.a
=
.~
~
'~
~,
DEGRADATION
[47]
of enzymes in cultured cells and serum are used in other laboratories. 44'4~ Deficiency of a-L-iduronidase, fl-galactosidase, or fl-hexosaminidase in cultured amniotic fluid cells may be used for the prenatal diagnosis of mucolipidosis II; the level of fl-hexosaminidase in the amniotic fluid is elevated. 46 44 J. H. Glaser, W. H. McAlister, and W. S. Sly, J. Pediatr. 85, 192 (1974), 4~ G. H. Thomas, H. A. Taylor, L. W. Reynolds, and C. S. Miller, Pediatr. Res. 7, 751 (1973). 46 p. Aula, J. Rapola, S. Autio, K. Raivio, and O. Karjalainen, J. Pediatr. 87,221 (1975).
[47] E n z y m i c D i a g n o s i s o f S p h i n g o l i p i d o s e s By
KUNIHIKO SUZUKI
The sphingolipidoses are defined as disorders of sphingolipid metabolism caused by genetic mutations of the hydrolytic enzymes which normally catabolize these sphingosine-containing lipids. Under this definition, two disorders are included for consideration in this section, although they do not involve metabolism of glycolipids. They are Niemann-Pick disease (sphingomyelinase deficiency) and Farber's lipogranulomatosis (ceramidase deficiency). On the other hand, the recently reported disease of ganglioside synthesis ~is not included under the above definition. The underlying genetic enzymic defects of the sphingolipidoses have now been largely clarified. Affected patients can be diagnosed definitively by appropriate enzyme assays, and heterozygous carriers of these diseases can be identified with reasonable reliability. In addition, in the majority of the sphingolipidoses, affected fetuses have been diagnosed during pregnancy by enzymic assays on cultured amniotic fluid cells. This section provides descriptions of reliable and practical procedures for enzymic diagnosis of the sphingolipidoses. For clinical, pathological, and analytical details of the individual diseases, the appropriate chapters in the book edited by Stanbury et al. 2 are suggested. A book that has a similar purpose as this section has also been published recently2 P. H. Fishman, S. R. Max, J. F. Tallman, R. O. Brady, N. K. Maclaren, and M. Corblath, Science 187, 68 (1975). 2 j. B. Stanbury, J. B. Wyngaarden, and D. S. Fredrickson (eds.), "The Metabolic Basis of Inherited Disease," 4th ed. McGraw-Hill, New York, 1978. a R. H. Glew and S. P. Peters (eds.), "Practical Enzymology of the Sphingolipidoses." Alan R. Liss, New York, in press.
[47]
457
E N Z Y M I C D I A G N O S I S OF S P H I N G O L I P I D O S E S
POLYSIALOGANGLIOSIDES
1
Ceramide - Glc - C~I- Gal- GalNAc
Ce ramide -GIc -Gal ~C.alNAc - Gal -~- ..... Ce ramide -Glc -C.el-(~tlNAc - Gel (GM])
Ceramide-Glc- Gal- Gal
Ceramide - GIc - Gal- C~INAc -9- . . . . . . . Ce ramide - GIe -Gal- GalNAc
-GIc-Gal ~
Ceramide -phospho rylchoUne
Cer!mideGlc
(Sphingomyelin)
(GI....... broside)
(~
" ~
~ ~_.._
Ceramide- GIc-Gal- NeuAc
c ~-~
(GM2)
(GM3)
ide- GRI- Gal
/
Ceramide-Gal ~ C e r a m i d e - C ~ l . S 0 4 (~
(C,~,act..... broside)
(~
(Sulfatide)
Sphlngosine
Flo. I. Chemical and metabolic relationship among major sphingolipids, and the locations of the genetic blocks. The numbers correspond to those in Tables I and II.
Diseases and Enzymic Defect The sphingolipids involved in the genetic sphingolipidoses can be systematically depicted in simplified notations as an interrelated series of compounds (Fig. 1). A specific genetic disease is known for every degradative step in Fig. 1, caused by the deficiency of the hydrolase that normally catalyzes that particular step, except for the steps involving desialylation of gangliosides (neuraminidase) and degradation of lactosylceramide (/3-galactosidase). These disorders are tabulated in Table I together with their clinicopathological characteristics, analytical abnormalities, and the affected enzymes. Enzyme Sources for Diagnostic Assays A variety of tissue sources can be utilized for the enzymic assays for diagnosis of the sphingolipidoses. Each source has its advantages and disadvantages. Solid tissues, such as brain, liver, spleen, or kidney, are generally excellent enzyme sources in cases in which antemortem diagnosis was not established. Almost all enzymes involved in the sphingolipidoses are sufficiently stable to allow reliable assays even with organs obtained 12 hr or longer after death. However, in view of other readily available specimens, solid tissue biopsies should no longer be permitted for the purpose of antemortem diagnosis of the sphingolipidoses. Serum is easily obtained and is a reliable source for some of the enzymes. However, the enzymic activities in serum are generally lower than those in cellular sources, and some of the enzymes cannot be assayed reliably in serum. Furthermore, some serum hydrolases appear to be less
458
[47]
DEGRADATION
.a
=
.~
~
'~
~,
