Document Detail

Action of intrinsic sialidase of rat brain synaptic membranes on membrane sialolipid and sialoprotein components in situ.
MedLine Citation:
PMID:  849935     Owner:  NLM     Status:  MEDLINE    
The sialo compounds in the synaptosomal membranes of young rat brain were specifically labeled in vivo by the intracranial injection of radioactive N-acetylmannosamine. More than 95% of the incorporated label was found in glycosidically bound sialic acid. Specific activities of sialic acid in the synaptic membrane gangliosides G71 (monosialo), GD1a (disialo), and GT1 (trisialo) were similar; labeling in GD1b (disialo) was consistently somewhat higher. The highest specific activity of rat brain sialidase was evenly distributed between "small myelin fragment" and synaptosomal membrane fractions, and ouabain-sensitive (Na+, K+)-ATPase also was concentrated in the latter fraction. The greatest amount of bound sialic acid was found in these subcellular fractions having the highest sialidase activity. A microsomal fraction was discovered to contain a small amount of bound sialic acid with a very high degree of radioactive labeling, but no sialidase. Release of sialic acid from the relatively intact membrane preparations by intrinsic membrane-bound sialidase occurred in two recognizable stages. There was a rapid initial release, complete within 30 min, of approximately equal amounts of lipid- and protein-bound sialic acid, corresponding to roughly half of the enzymatically releasable protein-boudn, and somewhat less than one-third of the lipid-bound, sialic acid. The remainder of the membrane sialidase-susceptible sialic acid was released in a second, slower stage. The intrinsic sialidase released 16 +/- 1% of the total sialoprotein and 31 +/- 1% of the total sialolipid sialic acid. Approximately the same amount of sialic acid is releasable from membrane sialolipid by the action of exogenous Vibrio sialidase; almost twice as much is releasable from sialoglycoprotein by this enzyme as compared with the intrinsic membrane sialidase. Each of the various membrane gangliosides appeared to be equally available to the action of the membrane sialidase. The results of this study indicate that both glycolipid- and glycoprotein-bound sialic acid in the synaptic membrane are releasable in situ by the action of the intrinsic synaptic membrane sialidase, and they suggest that this enzyme may act to modulate the physical properties of the membrane. In addition to influencing the rate of hydrolysis of endogenous membrane sialo compounds by intrinsic sialidase, pH had an effect on availability of protein-bound sialic acid. At acid pH, lipid- and protein-bound sialic acid were similarly available, but near neutral pH, gangliosides appeared to be attacked preferentially.
H C Yohe; A Rosenberg
Related Documents :
1259535 - The effect of gradual mild acid hydrolysis on serologic activities of glycoproteins fro...
11986305 - Psathyrella velutina mushroom lectin exhibits high affinity toward sialoglycoproteins p...
3192745 - Simple procedure for assessing relative quantities of neutral and acidic sugars in muci...
19719325 - Inhibition of neisseria meningitidis sialic acid synthase by a tetrahedral intermediate...
6020565 - Mechanism of fumaric acid accumulation in rhizopus nigricans.
10099405 - Quantitative enzymatic production of 1,6-diacyl sorbitol esters
Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  252     ISSN:  0021-9258     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  1977 Apr 
Date Detail:
Created Date:  1977-05-27     Completed Date:  1977-05-27     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  2412-8     Citation Subset:  IM    
Export Citation:
APA/MLA Format     Download EndNote     Download BibTex
MeSH Terms
Brain / enzymology*
Glycolipids / metabolism*
Microscopy, Electron
Nerve Tissue Proteins / metabolism
Neuraminidase / metabolism*
Sialoglycoproteins / metabolism*
Subcellular Fractions / enzymology
Synaptic Membranes / enzymology*,  ultrastructure
Reg. No./Substance:
0/Gangliosides; 0/Glycolipids; 0/Nerve Tissue Proteins; 0/Sialoglycoproteins; EC

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

Previous Document:  Preparation and properties of immobilized rubredoxin.
Next Document:  Biosynthesis of lipid-linked oligosaccharides in cotton fibers. Stimulation by lipids from pig liver...