Search results for "Aspartic acid"
showing 10 items of 87 documents
Evaluation of an amino acid residue critical for the specificity and activity of human Gb3/CD77 synthase
2016
Human Gb3/CD77 synthase (α1,4-galactosyltransferase) is the only known glycosyltransferase that changes acceptor specificity because of a point mutation. The enzyme, encoded by A4GALT locus, is responsible for biosynthesis of Gal(α1–4)Gal moiety in Gb3 (CD77, Pk antigen) and P1 glycosphingolipids. We showed before that a single nucleotide substitution c.631C > G in the open reading frame of A4GALT, resulting in replacement of glutamine with glutamic acid at position 211 (substitution p. Q211E), broadens the enzyme acceptor specificity, so it can not only attach galactose to another galactose but also to N-acetylgalactosamine. The latter reaction leads to synthesis of NOR antigens, which are…
Release of free amino acids upon oxidation of peptides and proteins by hydroxyl radicals
2017
Hydroxyl radical-induced oxidation of proteins and peptides can lead to the cleavage of the peptide, leading to a release of fragments. Here, we used high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) and pre-column online ortho-phthalaldehyde (OPA) derivatization-based amino acid analysis by HPLC with diode array detection and fluorescence detection to identify and quantify free amino acids released upon oxidation of proteins and peptides by hydroxyl radicals. Bovine serum albumin (BSA), ovalbumin (OVA) as model proteins, and synthetic tripeptides (comprised of varying compositions of the amino acids Gly, Ala, Ser, and Met) were used for reactions with hydroxyl ra…
Chronic aspartame intake causes changes in the trans-sulphuration pathway, glutathione depletion and liver damage in mice
2017
No-caloric sweeteners, such as aspartame, are widely used in various food and beverages to prevent the increasing rates of obesity and diabetes mellitus, acting as tools in helping control caloric intake. Aspartame is metabolized to phenylalanine, aspartic acid, and methanol. Our aim was to study the effect of chronic administration of aspartame on glutathione redox status and on the trans-sulphuration pathway in mouse liver. Mice were divided into three groups: control; treated daily with aspartame for 90 days; and treated with aspartame plus N-acetylcysteine (NAC). Chronic administration of aspartame increased plasma alanine aminotransferase (ALT) and aspartate aminotransferase activities…
Constitutive and regulated α-secretase cleavage of Alzheimer’s amyloid precursor protein by a disintegrin metalloprotease
1999
Amyloid β peptide (Aβ), the principal proteinaceous component of amyloid plaques in brains of Alzheimer’s disease patients, is derived by proteolytic cleavage of the amyloid precursor protein (APP). Proteolytic cleavage of APP by a putative α-secretase within the Aβ sequence precludes the formation of the amyloidogenic peptides and leads to the release of soluble APPsα into the medium. By overexpression ofa disintegrinandmetalloprotease (ADAM), classified as ADAM 10, in HEK 293 cells, basal and protein kinase C-stimulated α-secretase activity was increased severalfold. The proteolytically activated form of ADAM 10 was localized by cell surface biotinylation in the plasma membrane, but the m…
Down-regulation of Endogenous Amyloid Precursor Protein Processing due to Cellular Aging
2005
Processing of amyloid precursor protein (APP) is a well acknowledged central pathogenic mechanism in Alzheimer disease. However, influences of age-associated cellular alterations on the biochemistry of APP processing have not been studied in molecular detail so far. Here, we report that processing of endogenous APP is down-regulated during the aging of normal human fibroblasts (IMR-90). The generation of intracellular APP cleavage products C99, C83, and AICD gradually declines with increasing life span and is accompanied by a reduced secretion of soluble APP (sAPP) and sAPPalpha. Further, the maturation of APP was reduced in senescent cells, which has been shown to be directly mediated by a…
Neurochemical alterations in women with borderline personality disorder and comorbid attention-deficit hyperactivity disorder
2010
Borderline personality disorder (BPD) is associated with structural and functional brain changes. Recent models and findings refer to alterations of glutamate and total N-acetylaspartate (tNAA) in this condition.Absolute quantities of tNAA, creatine, glutamate, glutamine, myoinositol and total choline were measured using 3 Tesla magnetic resonance spectroscopy of the left anterior cingulate cortex and the left cerebellum in 14 unmedicated women with BPD and comorbid attention-deficit hyperactivity disorder (ADHD) and 18 healthy women. Both groups were matched with respect to age, education and premorbid intelligence.In the anterior cingulate, we found significantly higher tNAA and glutamate…
Evidence of Wallerian degeneration in normal appearing white matter in the early stages of relapsing-remitting multiple sclerosis
2003
Objective: Wallerian degeneration in normal appearing white matter in early relapsing-remitting multiple sclerosis (RRMS), and its correlation with the number of relapses and disease duration. Background Recent pathological studies have demonstrated Wallerian degeneration in normal appearing white matter (NAWM) in multiple sclerosis (MS), in established RRMS, and in chronic MS. However, the presence of Wallerian degeneration early in the disease and its correlation with relapse and with disease duration has not been studied. Methods: We performed proton magnetic resonance spectroscopic imaging in 21 MS patients, and 4 healthy controls, age and gender matched, aged under 45 years, with a max…
Cognitive impairment in multiple sclerosis can be predicted by imaging early in the disease.
2008
Background: Cognitive impairment is common in multiple sclerosis (MS) and adds significantly to the burden of the disease. The ability to predict future cognitive impairment from imaging obtained at disease onset has not been investigated. Methods: 62 patients imaged within 3 months of a clinically isolated syndrome were assessed neuropsychologically 7 years later. Baseline and periodic MRI measures of lesions, atrophy and normal-appearing white and grey matter were regressed against neuropsychological scores to explore the best predictors of cognitive outcome. Results: 28 patients had developed clinically definite MS at follow-up and a further nine met revised McDonald criteria for MS. Def…
Spectroscopic metabolomic abnormalities in the thalamus related to auditory hallucinations in patients with schizophrenia
2008
Abstract Objective Previous studies have found neurochemical abnormalities in thalamic nuclei in patients with schizophrenia. These abnormalities have been associated with information processing deficiencies and symptom formation. There are no metabolic spectroscopy studies in patients with schizophrenia attending to auditory hallucinations. The aim of the present study is to explore metabolic Magnetic Resonance Spectroscopy (MRS) ratio differences in the thalamus between schizophrenic patients with and without auditory hallucinations and control subjects. Methods MRS studies (MRI 1.5 T unit) were performed in 49 patients with schizophrenia (30 with auditory hallucinations and 19 without au…
Gly114Asp mutation of rhodopsin in autosomal dominant retinitis pigmentosa
1995
Two autosomal dominant retinitis pigmentosa families of different origin were screened for rhodopsin mutations using the method of single strand conformation polymorphism and direct sequencing. We found a CGG-CAG substitution in codon 114 of rhodopsin in both families. This change predicted the replacement of a glycine by an aspartic acid and suggested that this change is the cause of the disease in these families.