Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.4.1 (phosphodiesterase)
 18,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Acid sphingomyelinase (ASM; HGMW-approved symbol, SMPD1) is the lysosomal phosphodiesterase that hydrolyzes sphingomyelin to ceramide and phosphocholine. The deficient activity of this enzyme results in Types A and B Niemann-Pick disease (NPD). The full-length cDNA encoding human ASM has been isolated and characterized (E. H. Schuchman, M. Suchi, T. Takahashi, K. Sandhoff, and R. J. Desnick (1991) J. Biol. Chem. 66:8531-8539), and the ASM gene has been localized to chromosomal region 11p15.1-p15.4 (L. V. Pereira, R. J. Desnick, D. Adler, C. M. Disteche, and E. H. Schuchman (1991) Genomics 9:229-234). Using the cDNA as a probe, a genomic clone containing the ASM genomic region was isolated and the complete nucleotide sequence of the human ASM gene, including 1116 and 468 nucleotides upstream and downstream from the ASM coding region, respectively, was determined. This housekeeping gene contained six exons ranging in size from 77 to 773 bp and five introns ranging in size from 153 to 1059 bp. Exon 2 was unusually large and encoded 258 amino acids, or about 44% of the mature ASM polypeptide. The alternatively spliced 172-bp type 1-specific sequence was encoded by exon 3, whereas the type 2-specific sequence was located at the 5' end of intron 2. An analysis of the intron/exon junctions revealed that there was a weak donor splice site (AAA gtgagg) at the exon 3/intron 3 junction which occasionally leads to alternative splicing of exon 3 and the occurrence of the type 2 and 3 ASM transcripts. A single Alu1 element in the reverse orientation was in intron 2, immediately downstream from the type 2-specific sequence.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Structural organization and complete nucleotide sequence of the gene encoding human acid sphingomyelinase (SMPD1). 174 Mar 30

Human acid sphingomyelinase (SMPD1) is the lysosomal phosphodiesterase that cleaves sphingomyelin to ceramide and phosphocholine. The deficient activity of SMPD1 is the enzymatic defect in Types A and B Niemann-Pick disease. Previously, the gene encoding human SMPD1 was assigned to chromosome 17 by the differential thermostability of human and hamster SMPD1 in somatic cell hybrids. The recent isolation of the human SMPD1 cDNA (L. E. Quintern, E. H. Schuchman, O. Levran, M. Suchi, K. Ferlinz, H. Reinke, K. Sandhoff, and R. J. Desnick, 1989, EMBO J. 8: 2469-2473) permitted the mapping of this gene by molecular techniques. Oligonucleotide primers were synthesized to PCR amplify the human, but not murine, SMPD1 sequences in man-mouse somatic cell hybrids. In a panel of 15 hybrid cell lines, amplification of the human SMPD1 sequence was 100% concordant with the presence of human chromosome 11. For each of the other human chromosomes there were at least 6 discordant hybrid lines. Further analysis of somatic cell hybrids containing only chromosome 11 or chromosome 11 rearrangements localized the human SMPD1 gene to the region 11p15.1----p15.4. To provide an independent regional gene assignment, in situ hybridization was performed using the radiolabeled human SMPD1 cDNA. In the 58 metaphase cells examined, 34% of the 122 hybridization sites scored were located in the distal end of chromosome 11 with the major peak of hybridization at band 11p15. The absence of any other in situ hybridization site indicated the absence of pseudogenes or homologous sequences elsewhere in the genome. In contrast to the previous provisional localization to chromosome 17, these results assign a single locus for human SMPD1 to 11p15.1----p15.4.
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PMID:Regional assignment of the human acid sphingomyelinase gene (SMPD1) by PCR analysis of somatic cell hybrids and in situ hybridization to 11p15.1----p15.4. 200 72

During endocytosis, membrane components move to intraluminal vesicles of the endolysosomal compartment for digestion. At the late endosomes, cholesterol is sorted out mainly by two sterol-binding proteins, Niemann-Pick protein type C (NPC)1 and NPC2. To study the NPC2-mediated intervesicular cholesterol transfer, we developed a liposomal assay system. (Abdul-Hammed, M., B. Breiden, M. A. Adebayo, J. O. Babalola, G. Schwarzmann, and K. Sandhoff. 2010. Role of endosomal membrane lipids and NPC2 in cholesterol transfer and membrane fusion. J. Lipid Res. 51: 1747-1760.) Anionic lipids stimulate cholesterol transfer between liposomes while SM inhibits it, even in the presence of anionic bis(monoacylglycero)phosphate (BMP). Preincubation of vesicles containing SM with acid sphingomyelinase (ASM) (SM phosphodiesterase, EC 3.1.4.12) results in hydrolysis of SM to ceramide (Cer), which enhances cholesterol transfer. Besides SM, ASM also cleaves liposomal phosphatidylcholine. Anionic phospholipids derived from the plasma membrane (phosphatidylglycerol and phosphatidic acid) stimulate SM and phosphatidylcholine hydrolysis by ASM more effectively than BMP, which is generated during endocytosis. ASM-mediated hydrolysis of liposomal SM was also stimulated by incorporation of diacylglycerol (DAG), Cer, and free fatty acids into the liposomal membranes. Conversely, phosphatidylcholine hydrolysis was inhibited by incorporation of cholesterol, Cer, DAG, monoacylglycerol, and fatty acids. Our data suggest that SM degradation by ASM is required for physiological secretion of cholesterol from the late endosomal compartment, and is a key regulator of endolysosomal lipid digestion.
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PMID:Acid sphingomyelinase activity is regulated by membrane lipids and facilitates cholesterol transfer by NPC2. 2533 83