Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.24.27 (thermolysin)
 1,894 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Sphingosine-1-phosphate lyase is responsible for the ultimate step in sphingolipid breakdown, converting phosphorylated long chain bases into ethanolamine phosphate and a fatty aldehyde. Using tritiated dihydrosphingosine-1-phosphate, prepared enzymatically from [4,5-3H]dihydrosphingosylphosphocholine, we have reinvestigated the subcellular distribution of this enzyme in rat liver. Upon cell fractionation by differential centrifugation, the enzyme showed a microsomal distribution. Further separation of the microsomal fraction by sucrose gradient centrifugation confirmed an association with the endoplasmic reticulum. By means of constrained nonlinear regression, no evidence for a significant association with mitochondrial membranes, as reported previously (Stoffel, W., LeKim, D., and Sticht, G. (1969) Hoppe Seyler's Z. Physiol. Chem. 350, 1233-1241), nor with other cell compartments was found. The lyase activity, which appeared to be sensitive to different detergents, but not to Triton X-100, was not latent. It could be solubilized with Triton X-100, but not by high ionic strength, indicating that it is an integral membrane protein whose catalytic site is most probably exposed to the cytosol. Treatment of intact microsomal vesicles with trypsin or thermolysin inactivated the lyase activity, confirming that its catalytic site(s) or other domains essential for activity face the cytosol.
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PMID:Subcellular localization and membrane topology of sphingosine-1-phosphate lyase in rat liver. 206 24

The sites of the disulfide bonds in a napin protein isolated from Brassica napus have been identified by proteolytic cleavage and subsequent peptide mapping by matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS). Napins consist of two polypeptide chains containing two and six cysteine residues, respectively, that are held together by disulfide bonds. Upon initial cleavage of native napin by Endo-Lys-C, a disulfide-linked core complex of four peptides was obtained. This core peptide was isolated by reversed-phase HPLC and further digested by thermolysin, and the resulting fragments were identified by MALDI-MS. In a separate set of experiments, intact napin was subjected to proteolysis by thermolysin, and an isolated disulfide-linked peptide of interest was subdigested again using thermolysin. The combined data resulting from these experiments allowed the assignment of the disulfide linkages in a relatively abundant napin isoform, BngNAP1, apart from an ambiguity concerning the adjacent cysteines at positions 14' and 15' of the long chain. Two intermolecular disulfide bonds link Cys10 (short chain) with Cys25' (long chain) and Cys23 with Cys14' (or Cys15'), respectively. The long chain of napin contains two intramolecular disulfide bonds connecting Cys27' with Cys80' and Cys14' (or Cys15') with Cys72'.
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PMID:Assignment of the disulfide bonds in napin, a seed storage protein from Brassica napus, using matrix-assisted laser desorption ionization mass spectrometry. 904 25