2dob: Difference between revisions
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{{STRUCTURE_2dob| PDB=2dob | SCENE= }} | {{STRUCTURE_2dob| PDB=2dob | SCENE= }} | ||
===Crystal Structure of Human Saposin A=== | |||
{{ABSTRACT_PUBMED_16823039}} | |||
=== | ==Disease== | ||
[[http://www.uniprot.org/uniprot/SAP_HUMAN SAP_HUMAN]] Defects in PSAP are the cause of combined saposin deficiency (CSAPD) [MIM:[http://omim.org/entry/611721 611721]]; also known as prosaposin deficiency. CSAPD is due to absence of all saposins, leading to a fatal storage disorder with hepatosplenomegaly and severe neurological involvement.<ref>PMID:1371116</ref><ref>PMID:11309366</ref> Defects in PSAP saposin-B region are the cause of leukodystrophy metachromatic due to saposin-B deficiency (MLD-SAPB) [MIM:[http://omim.org/entry/249900 249900]]. MLD-SAPB is an atypical form of metachromatic leukodystrophy. It is characterized by tissue accumulation of cerebroside-3-sulfate, demyelination, periventricular white matter abnormalities, peripheral neuropathy. Additional neurological features include dysarthria, ataxic gait, psychomotr regression, seizures, cognitive decline and spastic quadriparesis. Defects in PSAP saposin-C region are the cause of atypical Gaucher disease (AGD) [MIM:[http://omim.org/entry/610539 610539]]. Affected individuals have marked glucosylceramide accumulation in the spleen without having a deficiency of glucosylceramide-beta glucosidase characteristic of classic Gaucher disease, a lysosomal storage disorder.<ref>PMID:2060627</ref><ref>PMID:17919309</ref> Defects in PSAP saposin-A region are the cause of atypical Krabbe disease (AKRD) [MIM:[http://omim.org/entry/611722 611722]]. AKRD is a disorder of galactosylceramide metabolism. AKRD features include progressive encephalopathy and abnormal myelination in the cerebral white matter resembling Krabbe disease.<ref>PMID:15773042</ref> Note=Defects in PSAP saposin-D region are found in a variant of Tay-Sachs disease (GM2-gangliosidosis). | |||
==Function== | |||
[[http://www.uniprot.org/uniprot/SAP_HUMAN SAP_HUMAN]] The lysosomal degradation of sphingolipids takes place by the sequential action of specific hydrolases. Some of these enzymes require specific low-molecular mass, non-enzymic proteins: the sphingolipids activator proteins (coproteins). Saposin-A and saposin-C stimulate the hydrolysis of glucosylceramide by beta-glucosylceramidase (EC 3.2.1.45) and galactosylceramide by beta-galactosylceramidase (EC 3.2.1.46). Saposin-C apparently acts by combining with the enzyme and acidic lipid to form an activated complex, rather than by solubilizing the substrate. Saposin-B stimulates the hydrolysis of galacto-cerebroside sulfate by arylsulfatase A (EC 3.1.6.8), GM1 gangliosides by beta-galactosidase (EC 3.2.1.23) and globotriaosylceramide by alpha-galactosidase A (EC 3.2.1.22). Saposin-B forms a solubilizing complex with the substrates of the sphingolipid hydrolases. Saposin-D is a specific sphingomyelin phosphodiesterase activator (EC 3.1.4.12). | |||
==About this Structure== | ==About this Structure== | ||
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==Reference== | ==Reference== | ||
<ref group="xtra">PMID:016823039</ref><references group="xtra"/> | <ref group="xtra">PMID:016823039</ref><references group="xtra"/><references/> | ||
[[Category: Homo sapiens]] | [[Category: Homo sapiens]] | ||
[[Category: Ahn, V E.]] | [[Category: Ahn, V E.]] | ||
