Xylosyltransferase II is the predominant isoenzyme which is responsible for the steady-state level of xylosyltransferase activity in human serum.

In mammals, two active xylosyltransferase isoenzymes (EC 2.4.2.

Large-scaled metabolic profiling of human dermal fibroblasts derived from pseudoxanthoma elasticum patients and healthy controls.

Mutations in the ABC transporter ABCC6 were recently identified as cause of Pseudoxanthoma elasticum (PXE), a rare genetic disorder characterized by progressive mineralization of elastic fibers. We used an untargeted metabolic approach to identify biochemical differences between human dermal fibroblasts from healthy controls and PXE patients in an attempt to find a link between ABCC6 deficiency, cellular metabolic alterations and disease pathogenesis. 358 compounds were identified by mass spectrometry covering lipids, amino acids, peptides, carbohydrates, nucleotides, vitamins and cofactors, xenobiotics and energy metabolites.

ABCC6- a new player in cellular cholesterol and lipoprotein metabolism?

Background: Dysregulations in cholesterol and lipid metabolism have been linked to human diseases like hypercholesterolemia, atherosclerosis or the metabolic syndrome. Many ABC transporters are involved in trafficking of metabolites derived from these pathways. Pseudoxanthoma elasticum (PXE), an autosomal-recessive disease caused by ABCC6 mutations, is characterized by atherogenesis and soft tissue calcification.

Variants in genes encoding pyrophosphate metabolizing enzymes are associated with Pseudoxanthoma elasticum.

Objectives: Pseudoxanthoma elasticum (PXE) is a rare hereditary disorder characterized by progressive calcification and fragmentation of elastic fibers. Because of the great clinical variability between PXE patients the involvement of modifier genes was recently suggested. Therefore, we investigated the association of single nucleotide variants (SNVs) in selected candidate genes known to regulate cellular pyrophosphate metabolism.

Pyrophosphates as a major inhibitor of matrix calcification in Pseudoxanthoma elasticum.

Background: Pseudoxanthoma elasticum (PXE) is a rare hereditary disorder characterized by late onset and progressive calcification of elastic fibers in skin, eyes and the cardiovascular system, exemplifying a model for conditions characterized by soft tissue calcification.

Objective: The aim of our study was to characterize cellular inorganic pyrophosphate (PPi) homeostasis in PXE.

Methods: Gene expression of PPi metabolizing enzymes was determined by quantitative real-time PCR after incubation up to 21 days with or without addition of Na2HPO4.

Measurement of HMG CoA reductase activity in different human cell lines by ultra-performance liquid chromatography tandem mass spectrometry.

Hydroxymethylglutaryl coenzyme A reductase (HMGCR) catalyzes the rate limiting step in cholesterol biosynthesis converting HMG-CoA into mevalonic acid (MVA), which equilibrates with mevalonic acid lactone (MVL) under neutral pH conditions. We developed a fast, sensitive, and efficient method to determine HMGCR activity in human cell lines measuring MVL levels by ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Convenient prepared samples containing MVL-D7 as an internal standard were injected, separated, and eluted from an ACQUITY HSS PFP column.