Related Experiment Video
Updated: Apr 18, 2026
Click-Chemistry Based Fluorometric Assay for Apolipoprotein N-acyltransferase from Enzyme Characterization to High-Throughput Screening
Published on: May 13, 2020
A fast semi-quantitative LC-MS method for measurement of intact apolipoprotein A-I reveals novel proteoforms in serum
1Unit of Clinical Chemistry, Department of Laboratory Medicine, Lund University, S-22185 Lund, Sweden.
Background:
Surrogate markers for reverse cholesterol transport (RCT) efficiency such as HDL cholesterol and immune methods for apolipoprotein A-I (ApoA-I) may not fully reflect the actual efficiency of the RCT pathway. Several genetic variants and different posttranslational proteoforms of ApoA-I may unevenly affect the functionality of the HDL particle to efflux cholesterol. A method employing top-down immunoaffinity LC-MS of ApoA-I in order to characterize the most prevalent ApoA-I proteoforms in human plasma is described.
Methods:
Diluted plasma was directly injected into a 2D LC-MS system consisting of an affinity column and an analytical column. Enriched ApoA-I fractions were introduced into the MS and intact or fragmented ApoA-I was analyzed.
Results:
ApoA-I as detected by the described LC-MS method distributes into at least 14 major potential proteoforms exceeding detection limit in human plasma. Substantial amounts of ApoA-I in plasma were found to occur as truncated, oxidized, glycated and glycosylated proteoforms. Levels of glycated ApoA-I distinguished significantly diabetic from non-diabetic samples. In addition novel truncated and glycosylated proteoforms were detected.
Conclusions:
ApoA-I proteoforms measured by LC-MS represent a useful approach to augment the clinical picture of ApoA-I and its function in health and disease.
