Publications

• Purification, characterization, and biosynthesis of human acid ceramidase.

  Bernardo K., Hurwitz R., Zenk T., Desnick R.J., Ferlinz K., Schuchman E.H., Sandhoff K.

  Acid ceramidase (N-acylsphingosine deacylase, EC 3.5.1.23) is the lysosomal enzyme catalyzing the hydrolysis of ceramide to sphingosine and free fatty acid. Its inherited deficiency causes ceramide accumulation in Farber's disease. The enzyme was purified to apparent homogeneity from human urine b ... >> More

  Acid ceramidase (N-acylsphingosine deacylase, EC 3.5.1.23) is the lysosomal enzyme catalyzing the hydrolysis of ceramide to sphingosine and free fatty acid. Its inherited deficiency causes ceramide accumulation in Farber's disease. The enzyme was purified to apparent homogeneity from human urine by sequential chromatography on octyl-Sepharose, concanavalin A-Sepharose, blue-Sepharose, and DEAE-cellulose. The final preparation, which was enriched approximately 4450-fold over the starting material, resulted in a polypeptide of approximately 50 kDa and could be reduced into two subunits of approximately 13 (alpha) and approximately 40 (beta) kDa. Treatment of the purified enzyme with endoglycosidase H or peptido-N-glycanase F reduced the molecular mass of the beta subunit to approximately 30-35 and approximately 27 kDa, respectively. In contrast, the molecular mass of the alpha subunit was unchanged. The purified enzyme had an apparent Km of 149 microM and a Vmax of 136 nmol/mg/h using N-lauroylsphingosine as substrate. Polyclonal antibodies were raised against the purified urinary enzyme and used to investigate the biosynthesis of acid ceramidase. Immunoprecipitation studies on metabolically labeled skin fibroblasts indicated that both subunits arose from a single precursor of approximately 55 kDa. A minor portion of newly synthesized acid ceramidase was secreted into the medium as a monomeric 47-kDa protein, indicating that generation of the mature heterodimeric enzyme occurred in endosomal and/or lysosomal compartments. << Less

  J. Biol. Chem. 270:11098-11102(1995) [PubMed] [EuropePMC]

  This publication is cited by 5 other entries.

• Substrate specificity, membrane topology, and activity regulation of human alkaline ceramidase 2 (ACER2).

  Sun W., Jin J., Xu R., Hu W., Szulc Z.M., Bielawski J., Obeid L.M., Mao C.

  Human alkaline ceramidase 2 (ACER2) plays an important role in cellular responses by regulating the hydrolysis of ceramides in cells. Here we report its biochemical characterization, membrane topology, and activity regulation. Recombinant ACER2 was expressed in yeast mutant cells (Deltaypc1Deltayd ... >> More

  Human alkaline ceramidase 2 (ACER2) plays an important role in cellular responses by regulating the hydrolysis of ceramides in cells. Here we report its biochemical characterization, membrane topology, and activity regulation. Recombinant ACER2 was expressed in yeast mutant cells (Deltaypc1Deltaydc1) that lack endogenous ceramidase activity, and microsomes from ACER2-expressiong yeast cells were used to biochemically characterize ACER2. ACER2 catalyzed the hydrolysis of various ceramides and followed Michaelis-Menten kinetics. ACER2 required Ca(2+) for both its in vitro and cellular activities. ACER2 has 7 putative transmembrane domains, and its amino (N) and carboxyl (C) termini were found to be oriented in the lumen of the Golgi complex and cytosol, respectively. ACER2 mutant (ACER2DeltaN36) lacking the N-terminal tail (the first 36 amino acid residues) exhibited undetectable activity and was mislocalized to the endoplasmic reticulum, suggesting that the N-terminal tail is necessary for both ACER2 activity and Golgi localization. ACER2 mutant (ACER2DeltaN13) lacking the first 13 residues was also mislocalized to the endoplasmic reticulum although it retained ceramidase activity. Overexpression of ACER2, ACER2DeltaN13, but not ACER2DeltaN36 increased the release of sphingosine 1-phosphate from cells, suggesting that its mislocalization does not affect the ability of ACER2 to regulate sphingosine 1-phosphate secretion. However, overexpression of ACER2 but not ACER2DeltaN13 or ACER2DeltaN36 inhibited the glycosylation of integrin beta1 subunit and Lamp1, suggesting that its mistargeting abolishes the ability of ACER2 to regulation protein glycosylation. These data suggest that ACER2 has broad substrate specificity and requires Ca(2+) for its activity and that ACER2 has the cytosolic C terminus and luminal N terminus, which are essential for its activity, correct cellular localization, and regulation for protein glycosylation. << Less

  J. Biol. Chem. 285:8995-9007(2010) [PubMed] [EuropePMC]

  This publication is cited by 7 other entries.

• Expression, purification, and characterization of a recombinant neutral ceramidase from Mycobacterium tuberculosis.

  Okino N., Ikeda R., Ito M.

  Ceramidase (CDase) catalyzes the hydrolysis of ceramide (Cer) to sphingosine (Sph) and fatty acid. We have reported the molecular cloning and preliminary characterization of the Mycobacterium CDase (MtCDase) (J. Biol. Chem., 274, 36616-36622 (1999)). To determine its function further, MtCDase was ... >> More

  Ceramidase (CDase) catalyzes the hydrolysis of ceramide (Cer) to sphingosine (Sph) and fatty acid. We have reported the molecular cloning and preliminary characterization of the Mycobacterium CDase (MtCDase) (J. Biol. Chem., 274, 36616-36622 (1999)). To determine its function further, MtCDase was expressed in Escherichia coli and purified by Ni-Sepharose and gelfiltration. The purified recombinant enzyme showed a single band and a molecular weight estimated to be 71 kDa on SDS-PAGE. It had a pH optimum at 8.0-9.0 and quite broad specificity for various Cers. Of the Cers of different fatty acid moieties tested, those composed of C6-C24 fatty acids were well hydrolyzed, and Cers with mono unsaturated fatty acids were much more hydrolyzed than those with saturated fatty acids. Using N-dodecanoyl-7-nitrobenz-2-oxa-1,3-4-diazole (NBD)-D-erythro-sphingosine (C12-NBD-Cer) as substrates, the reaction followed normal Michaelis-Menten kinetics. The apparent Km and Vmax values for C12-NBD-Cer were 98.7 muM and 21.1 pmol/min respectively. The purified enzyme also catalyzed the synthesis of Cer in vitro, using NBD-labeled dodecanoic acid and Sph as substrates. << Less

  Biosci. Biotechnol. Biochem. 74:316-321(2010) [PubMed] [EuropePMC]

  This publication is cited by 9 other entries.