Synthesis and processing of sphingolipid activator protein-2 (SAP-2) in cultured human fibroblasts
Sphingolipid activator proteins (SAP) are relatively small molecular weight proteins that stimulate the enzymatic hydrolysis of sphingolipids in the presence of specific lysosomal hydrolases. SAP-2 has previously been demonstrated to activate the hydrolysis of glucosylceramide, galactosylceramide, and, possibly, sphingomyelin. Using monospecific rabbit antibodies against human spleen SAP-2, the synthesis and processing of SAP-2 were studied in cultured human fibroblasts. When (/sup 35/S)methionine was presented in the medium to control human cells for 4 h, five major areas of radiolabeling were found. These had apparent molecular weights of 73,000, 68,000, 50,000, 12,000, and 9000. Further studies indicated that the major extracellular product in normal cells given NH4Cl along with the (/sup 35/S)methionine and in medium from cultures from patients with I cell disease had an apparent molecular weight of 73,000. The Mr = 68,000 and 73,000 species can be converted to a species with an apparent molecular weight of 50,000 by the action of endoglycosidase F. After labeling cells for 1 h followed by a 1-h chase, the Mr = 12,000 and 9000 species appear. Treatment of the immunoprecipitated mixture with endoglycosidase F resulted in conversion of these species to one band with an apparent molecular weight of 7600. These studies indicate that this relatively low molecular weight protein is rapidly synthesized from a relatively large molecular weight highly glycosylated precursor.
- Research Organization:
- Univ. of Colorado School of Medicine, Denver
- OSTI ID:
- 6851486
- Journal Information:
- J. Biol. Chem.; (United States), Vol. 32
- Country of Publication:
- United States
- Language:
- English
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PROTEINS
MOLECULAR WEIGHT
AMMONIUM COMPOUNDS
CELL CULTURES
CHLORIDES
FIBROBLASTS
HYDROLASES
HYDROLYSIS
LABELLED COMPOUNDS
LIPIDS
METHIONINE
SKIN
SULFUR 35
TRACER TECHNIQUES
AMINO ACIDS
ANIMAL CELLS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BODY
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
CHLORINE COMPOUNDS
CONNECTIVE TISSUE CELLS
DAYS LIVING RADIOISOTOPES
DECOMPOSITION
DRUGS
ENZYMES
EVEN-ODD NUCLEI
HALIDES
HALOGEN COMPOUNDS
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
LIPOTROPIC FACTORS
LYSIS
NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
ORGANS
RADIOISOTOPES
SOLVOLYSIS
SOMATIC CELLS
SULFUR ISOTOPES
550201* - Biochemistry- Tracer Techniques