20 research outputs found
Levels of uroporphyrinogen decarboxylase (URO-D) in erythocytes of Italian porphyria cutanea tarda patients
No full textPorphyria cutanea tarda (PCT) is a human metabolic disorder due to the acquired or genetic impairment of uroporphyrinogen decarboxylase (URO-D) activity, the fifth enzyme of the heme biosynthetic pathway. A classification of inherited and non-inherited forms is based on the enzyme activity levels in red blood cells (RBC). Clinical manifestations of PCT are often precipitated by triggering factors such as alcohol, drug abuse, estrogens, virus infections, hepatotoxic chemicals and hepatic siderosis. We measured URO-D activity in RBC from a large sample of Italian PCT patients in order to define the enzyme activity distribution and to attempt a correlation among activity, risk factors and clinical outcome. Three classes of patients with low, normal and over-normal URO-D activity were defined according to control values. Low URO-D levels were present in 25.8% of patients, suggesting the familial form of PCT (type II). In this group, the outcome of PCT seems to be less influenced by risk factors. Patients with over-normal URO-D activity in RBC deserve further investigation
Chronic non-spherocytic haemolytic disorders associated with glucose-6-phosphate dehydrogenase variants
No full textGlucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common human enzyme defect, being present in over 400 million people world wide. In a small number of cases, G6PD deficiency can lead to mild-to-severe chronic haemolysis, which is further exacerbated by oxidative stress. Such G6PD variants have been described all over the world and are responsible for chronic non-spherocytic haemolytic anaemia (CNSHA). To date 61 G6PD molecular variants associated with CNSHA have been identified, only some of which can cause the severe reduction in stability of the red blood cell enzyme. The distribution of the different mutations shows a predominance of small mutational events, and many have been found repeatedly in different parts of the world. By revisiting the 61 class I variants described so far, we can observe that a low inhibition constant (Ki) for NADPH, a higher Km for substrates and a reduced thermostability are commo
Acute intermittent porphyria: Heterogeneity of mutations in the hydroxymethylbilane synthase gene in Italy
No full textAcute intermittent porphyria (AIP) is an autosomal disorder caused by molecular abnormalities in the gene coding for hydroxymethylbilane synthase (HMBS), the third enzyme in the heme biosynthetic pathway. So far, more than 170 different mutations responsible for AIP have been identified worldwide in the HMBS gene. In this study we have performed molecular characterization in 14 patients with suspected diagnosis of AIP and in 29 family members of Italian ancestry. Molecular analysis of the HMBS gene allowed us to identify 13 different mutations among 14 patients with reduced HMBS activity: 5 splicing defects (IVS9+22 G>A, 612 G>T, IVS 11-2 delA, IVS 12 + 2 T>C, and IVS 13-1 G>A), 1 small insertion (182 insGA), I small deletion (730-731 delCT), and 6 missense/nonsense mutations (76 C>T, 295 G>A, 331 G>A, 580 C>T. 673 C>T, and 874 C>T), resulting in single-amino-acid substitutions or protein truncations. Six of these molecular abnormalities had already been described and 7 are new findings. In a previous work on an Italian population we detected 7 different mutations among 8 AIP patients. This study has raised to 18 the number of different mutations so far found among the Italian AIP population, I I of which are new findings. We can conclude that the mutation screening in the Italian population contributes to improvement of the diagnostic approach of AIP and to establishing possible clustering of mutations in the Mediterranean area
The expression of uridine diphosphate glucuronosyltransferase gene is a major determinant of bilirubin level in heterozygous beta-thalassaemia and in glucose-6-phosphate dehydrogenase deficiency
No full textWe evaluated the effect of Gilbert's syndrome, the most common defect of bilirubin conjugation, on the bilirubin levels of subjects with inherited haematological disorders which cause increased bilirubin production. 57 patients heterozygous for beta-thalassaemia, 21 with G6PD deficiency and 44 controls were examined by typing the TATA-box in the promoter of the gene uridine diphosphate glucuronosyltransferase 1A. Nearly 80% of patients with increased bilirubin levels were heterozygous or homozygous for the UGT1A TA(7) variant associated with Gilbert's syndrome. These findings indicate that Gilbert's syndrome accounts for a large proportion of the variability of bilirubin levels in beta-thalassaemia and G6PD deficiency
G6PD Ferrara I has the same two mutations as G6PD A(-) but a distinct biochemical phenotype
No full textThe cloning and sequencing of the normal glucose-6-phosphate dehydrogenase (G6PD) gene has led to the study of the molecular defects that determine enzymatic variants. In this paper, we describe the mutations responsible for the Ferrara I variant in an Italian man with a family history of favism, from the Po delta. Nucleotide sequencing of this variant showed a G→A mutation at nucleotide 202 in exon IV causing a Val→Met amino acid exchange, and a second A→G mutation at nucleotide 376 in exon V causing an Asn→Asp amino acid substitution. Although on the basis of its biochemical properties this variant was classified as G6PD Ferrara I, it has the same two mutations as G6PD A(-), which is common in American and African blacks, and as the sporadic Italian G6PD Matera. The mutation at nucleotide 202 was confirmed by NlaIII digestion of a polymerase chain reaction amplified DNA fragment spanning 109 bp of exon IV. The 109-bp mutated amplified sequence is not distinguishable from the normal sequence in single strand conformation polymorphism analysis
Molecular characterisation of the glucose-6-phosphate dehydrogenase (G6PD) Ferrara II variant
No full textDuring the last ten years, molecular biological techniques such as cloning and sequencing and, more recently, polymerase chain reaction (PCR) amplification have led to the identification of the molecular defects responsible for more than fifty glucose-6-phosphate dehydrogenase (G6PD) variants. In this paper, we report the identification of the molecular abnormality underlying the G6PD Ferrara II variant, present in the Po delta area of Northern Italy. Biochemical characterisation shows an enzymatic activity of about 15% of normal (WHO class III), slow electrophoretic mobility, low Km for G6P, high percentage substrate analogue utilisation and a biphasic pH optimum curve. After PCR amplification, non-radioiso-topic single-strand conformation polymorphism analysis carried out for the entire coding region has revealed a mobility shift in exon 8. Nucleotide sequencing has demonstrated a missense 844 G>C mutation, causing an Asp>His amino-acid replacement, known as being responsible for G6PD Seattle, G6PD Modena and G6PD Lodi
