Distinct glycoforms of human alpha1-acid glycoprotein have comparable synthesis rates: a [13C]valine-labelling study in healthy humans.
Various alpha1-acid glycoprotein (AGP) glycoforms are present in plasma differing in extent of branching and/or fucosylation of their 5 N-linked glycans, as well as in concentration. It is assumed that hepatic synthesis determines the relative occurrence of the AGP-glycoforms in plasma, but experimental evidence is lacking. In this study, we have investigated the contribution of fractional synthesis rates to the plasma concentration of AGP-glycoforms that differed in relative occurrence in healthy human plasma. During a [13C]valine infusion, AGP was isolated from the plasma of healthy volunteers. Four AGP-glycoforms, differing strongly in plasma concentration were obtained by sequential affinity chromatography over concanavalin-A- and Aleuria aurantia -agarose columns. The incorporation of the [13C]valine tracer into the AGP-glycoforms was measured by gas chromatography combustion isotope ratio mass spectrometry. The mean fractional synthesis rates of the four AGP-glycoforms did not differ significantly between each other as well between individuals. The results indicated a renewal of about 15%/day of the plasma pools of each of the AGP-glycoforms. This is in support to the assumption that the differences in plasma concentration of the AGP-glycoforms are a reflection of the state of the hepatic glycosylation process.
Glycoimmunology Group, Department of Molecular Cell Biology & Immunology, VU Medical Center, Amsterdam, The Netherlands.
Dennis C W
DC
Poland
Willem
W
Kulik
Willem
W
van Dijk
Marcella M
MM
Hallemeesch
Cornelis
C
Jakobs
Kees
K
de Meer
D000328:Adult; D002247:Carbon Isotopes; D006801:Humans; D008297:Male; D009961:Orosomucoid / Q000096:biosynthesis*; D013997:Time Factors; D014633:Valine / Q000378:metabolism*
D002247:Carbon Isotopes; D009961:Orosomucoid; D014633:Valine