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ISOLATION AND CHARACTERIZATION OF A SOLUBLE GLUCOSE‐CONTAINING SIALOGLYCOPROTEIN FROM THE CORTICAL GREY MATTER OF CALF BRAIN
Author(s) -
Amerongen A. van Nieuw,
Eijnden D. H. van den,
Heijlman J.,
Roukema P. A.
Publication year - 1972
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1972.tb05128.x
Subject(s) - sialoglycoprotein , sialic acid , biochemistry , chromatography , chemistry , hexose , percoll , carbohydrate , polyacrylamide gel electrophoresis , neuraminic acid , ganglioside , amino acid , centrifugation , aspartic acid , biology , enzyme
A sialoglycoprotein has been isolated from the cortical grey matter of calf brain after homogenization in 0.32 M‐sucrose or in 0.15 M‐NaCl. The sialoglycoprotein is present in the supernatant obtained after centrifugation at 100,000 g for 60 min. It is designated GP‐350 on account of its elution with 350 mM‐NaCl on a DEAE‐cellulose column. From DEAE‐cellulose chromatography it is evident that compounds comparable to GP‐350 occur in the brain of calf and sheep, whereas they seem to be absent in calf liver and kidney. After purification, with polyacrylamide gel electrophoresis only one band can be shown both at pH 8.9 and 7.5. GP‐350 consists of about 83 percent of protein and about 17 per cent of carbohydrate. The polypeptide core has an acidic character: amino acid analysis gives 26 per cent for glutamic acid plus aspartic acid and their amides, with a ratio of acidic to basic amino acids of 3.3. The carbohydrate moiety contains 2.4% sialic acid, 5.5 % hexosamine and 9.4% hexose. It is remarkable that this brain sialoglycoprotein comprises 4% glucose. Care was taken to prevent contamination with glucose‐containing materials during the purification procedure of GP‐350. The complete absence of other glucose‐containing compounds which occur in brain, Le. glycogen and gangliosides, was demonstrated. GP‐350 accounts for at least 3 per cent of the total saline‐extractable protein and about 20 per cent of the total saline‐extractable protein‐bound sialic acid of the cortical grey matter of calf brain. These percentages correspond to 390 pg of protein and to 14 μg of sialic acid per g wet weight. GP‐350 remains soluble when the pH is brought to 3.9 or when ethanol is added to 70 % (v/v).