Biomaterial Database

Non-enzymatic glycosylation of plasma lipoproteins in vitro. 1985

C C Smith, and A C Dickson, and D J Betteridge

Human very low density lipoprotein (VLDL), low density lipoprotein (LDL) and high density lipoproteins (HDL2 and HDL3) were glycosylated in vitro by incubation with high concentrations of glucose and glucose-6-phosphate. Glycosylated lipoproteins showed enhanced mobility on agarose electrophoresis when compared to control lipoproteins, samples treated with glucose-6-phosphate being more strongly affected. Extent of glycosylation of LDL was determined using thiobarbituric acid, LDL incubated with glucose exhibiting degrees of glycosylation 15-117% in excess of control. LDL incubated with glucose-6-phosphate however, gave values similar to those obtained with control incubations. Amino acid analysis of protein hydrolysates prepared from VLDL and LDL fractions incubated with glucose revealed reductions of up to 53% in the levels of free lysine when compared to control lipoprotein samples. The appearance of 2 novel peaks, probably corresponding to glucosyllysine, was also observed. The effects seen with glucose-6-phosphate however, were not as marked as expected. None of the other amino acids measured were decreased. These data show that plasma lipoproteins can be glycosylated in vitro and that an indication of the degree of glycosylation (by glucose) may be obtainable using thiobarbituric acid. Amino acid analysis revealed that the probable binding site for glucose on the apoproteins are the lysine residues. Although glucose-6-phosphate also binds to lysine residues the effects produced by this agent on plasma lipoproteins may also involve other mechanisms requiring further investigation.

UI	MeSH Term	Description	Entries
D008075	Lipoproteins, HDL	A class of lipoproteins of small size (4-13 nm) and dense (greater than 1.063 g/ml) particles. HDL lipoproteins, synthesized in the liver without a lipid core, accumulate cholesterol esters from peripheral tissues and transport them to the liver for re-utilization or elimination from the body (the reverse cholesterol transport). Their major protein component is APOLIPOPROTEIN A-I. HDL also shuttle APOLIPOPROTEINS C and APOLIPOPROTEINS E to and from triglyceride-rich lipoproteins during their catabolism. HDL plasma level has been inversely correlated with the risk of cardiovascular diseases.	High Density Lipoprotein,High-Density Lipoprotein,High-Density Lipoproteins,alpha-Lipoprotein,alpha-Lipoproteins,Heavy Lipoproteins,alpha-1 Lipoprotein,Density Lipoprotein, High,HDL Lipoproteins,High Density Lipoproteins,Lipoprotein, High Density,Lipoprotein, High-Density,Lipoproteins, Heavy,Lipoproteins, High-Density,alpha Lipoprotein,alpha Lipoproteins
D008077	Lipoproteins, LDL	A class of lipoproteins of small size (18-25 nm) and light (1.019-1.063 g/ml) particles with a core composed mainly of CHOLESTEROL ESTERS and smaller amounts of TRIGLYCERIDES. The surface monolayer consists mostly of PHOSPHOLIPIDS, a single copy of APOLIPOPROTEIN B-100, and free cholesterol molecules. The main LDL function is to transport cholesterol and cholesterol esters to extrahepatic tissues.	Low-Density Lipoprotein,Low-Density Lipoproteins,beta-Lipoprotein,beta-Lipoproteins,LDL(1),LDL(2),LDL-1,LDL-2,LDL1,LDL2,Low-Density Lipoprotein 1,Low-Density Lipoprotein 2,LDL Lipoproteins,Lipoprotein, Low-Density,Lipoproteins, Low-Density,Low Density Lipoprotein,Low Density Lipoprotein 1,Low Density Lipoprotein 2,Low Density Lipoproteins,beta Lipoprotein,beta Lipoproteins
D008079	Lipoproteins, VLDL	A class of lipoproteins of very light (0.93-1.006 g/ml) large size (30-80 nm) particles with a core composed mainly of TRIGLYCERIDES and a surface monolayer of PHOSPHOLIPIDS and CHOLESTEROL into which are imbedded the apolipoproteins B, E, and C. VLDL facilitates the transport of endogenously made triglycerides to extrahepatic tissues. As triglycerides and Apo C are removed, VLDL is converted to INTERMEDIATE-DENSITY LIPOPROTEINS, then to LOW-DENSITY LIPOPROTEINS from which cholesterol is delivered to the extrahepatic tissues.	Pre-beta-Lipoprotein,Prebeta-Lipoprotein,Prebeta-Lipoproteins,Very Low Density Lipoprotein,Very-Low-Density Lipoprotein,Very-Low-Density Lipoproteins,Lipoprotein VLDL II,Lipoproteins, VLDL I,Lipoproteins, VLDL III,Lipoproteins, VLDL1,Lipoproteins, VLDL2,Lipoproteins, VLDL3,Pre-beta-Lipoproteins,Lipoprotein, Very-Low-Density,Lipoproteins, Very-Low-Density,Pre beta Lipoprotein,Pre beta Lipoproteins,Prebeta Lipoprotein,Prebeta Lipoproteins,VLDL Lipoproteins,VLDL1 Lipoproteins,VLDL2 Lipoproteins,VLDL3 Lipoproteins,Very Low Density Lipoproteins
D004587	Electrophoresis, Agar Gel	Electrophoresis in which agar or agarose gel is used as the diffusion medium.	Electrophoresis, Agarose Gel,Agar Gel Electrophoresis,Agarose Gel Electrophoresis,Gel Electrophoresis, Agar,Gel Electrophoresis, Agarose
D005947	Glucose	A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement.	Dextrose,Anhydrous Dextrose,D-Glucose,Glucose Monohydrate,Glucose, (DL)-Isomer,Glucose, (alpha-D)-Isomer,Glucose, (beta-D)-Isomer,D Glucose,Dextrose, Anhydrous,Monohydrate, Glucose
D005958	Glucosephosphates
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000596	Amino Acids	Organic compounds that generally contain an amino (-NH2) and a carboxyl (-COOH) group. Twenty alpha-amino acids are the subunits which are polymerized to form proteins.	Amino Acid,Acid, Amino,Acids, Amino
D013858	Thiobarbiturates	Compounds in which one or more of the ketone groups on the pyrimidine ring of barbituric acid are replaced by thione groups.
D053439	Lipoproteins, HDL2	Low-density subclass of the high-density lipoproteins, with particle sizes between 8 to 13 nm.	High Density Lipoprotein-2,HDL-2,HDL2 Lipoprotein,High Density Lipoprotein HDL2,Lipoprotein HDL2,HDL 2,HDL2 Lipoproteins,HDL2, Lipoprotein,High Density Lipoprotein 2,Lipoprotein, HDL2