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Biomedical subjects

G Romeo

Publications and source records attributed to G Romeo.

At least 325 records · Page 18Linked to original sources
PubMed1979

5'-Methylthioadenosine phosphorylase from Caldariella acidophila. Purification and properties.

The occurrence of 5'-methylthioadenosine phosphorylase in Caldariella acidophila, a thermophilic bacterium growing optimally at 87 degrees C, is reported. It represents the first example in prokaryotes of a phosphoryolytic cleavage of the thioether. The reaction products, purified by ion-exchange chromatography, have been identified as 5-methylthioribose-1-phosphate and adenine by several analytical procedures. The enzyme has been purified to homogeneity in 32% yield by using DEAE-cellulose and hydroxyapatite chromatography, gel filtration and isoelectric focusing. The enzyme shows a high degree of thermophilicity, its temperature optimum being at 93 degrees C; furthermore no loss of activity is observable after exposure for 1 h at 100 degrees C. The kinetic data indicate a sequential mechanism of the reaction. The apparent Km values are 0.095 mM for 5'-methylthioadenosine and 6.1 mM for phosphate. The specificity of the reaction is rather strict. Experiments performed with analogues of the substrate, i.e. 5'-methylthioinosine, 5'-dimethylthioadenosine sulfonium salt, 5'-n-butylthioadenosine, 5'-isobutylthioadenosine, 5'-isobutylthioinosine, adenosylhomocysteine, 5'-thioethanoladenosine, adenosine, indicate the relevance of the adenine amino group and the sulfur in thioether form in the binding to the enzyme protein.

Adenosine↗
PubMed1979

Binding of 125I-labeled proteinases to plasma proteins in cystic fibrosis.

Samples of plasma or serum from 53 cystic fibrosis (CF) patients, 90 relatives of CF patients , and 159 controls have been incubated with porcine or bovine 125I-trypsin, electrophoresed on polyacrylamide gel, and autoradiographed. In these individuals, the main binding protein for 125I-trypsin has been shown to be alpha 2-macroglobulin (alpha 2M). Using this method of analysis, no difference in electrophoretic migration of 125I-trypsin-alpha 2M complexes has been observed between CF and control individuals. However, trypsin binding to IgG has been observed in 80% of CF patients, 30% of their mothers, 3% of controls, and in two patients affected with pancreatitis. These trypsin binding immunoglobulins are called TbIg, and specifically, Tb1gG when referring to the G class. Experimental evidence indicates that binding of trypsin to IgG occurs through the Fab portion of the molecule. Tb1gG must be antibodies most probably induced by the exogenous trypsin ingested daily by most CF patients (and by patients affected with chronic pancreatitis). Antibodies against porcine pancreatic elastase have been observed using the same analysis, but not as frequently as Tb1g.

Arginine↗
PubMed1978

[5'-methylthioadenosine phosphorylase from Caldariella acidophila. 1. Purification and partial characterization].

5'-Methylthioadenosine phosphorylase has been isolated from C.acidophila, a thermophilic bacterium living in acid hot springs at temperatures ranging from 63 to 89 degrees C. The enzyme has been purified to homogeneity in 32% yield. The enzyme shows a high degree of thermophilicity, its temperature optimum being 93 degrees C in the in vitro assay. The enzyme is exceptionally stable; no loss of activity was observable after exposure for 1 h at 100 degrees C. The optimum pH is about 7,2, with one-half of the maximal activity occurring at pH 6 and 9. The apparent Km for the substrates are: 8,3 x 10(-5) M for MTA and 4,3 x 10(-4) M for phosphate ions.

Adenosine↗
PubMed1977

Enzymatic defects of hereditary porphyrias: an explanation of dominance at the molecular level.

In four of the five autosomal dominant porphyrias four different partial enzymatic defects of the porphyrin biosynthetic pathway have been discovered in the last few years. With the exception of protoporphyria, the residual enzymatic activity in carriers of these defects is approximately equal to 50% of that found in controls. In each case the pattern of excretion of porphyrin and/or porphyrin precursors reflects the stie of the partial metabolic block. There are indications, at least in intermittent acute porphyria, that the degree of penetrance of the disorder varies according to the level of phenotypic expression, being highest for the enzyme deficiency, lower for the excretion of precursors and lowest for the clinical symptoms. It is proposed that environmental factors, and probably also gene interaction, are the cause of the different degrees of penetrance.

5-Aminolevulinate Synthetase↗
PubMed1977

Heterogeneity of nonlethal severe short-limbed dwarfism.

The Grebe syndrome is a nonlethal form of severe short-limbed dwarfism which was previously called "achondrogenesis-Brazilian or Grebe type". We have studied three patients with severe short-limbed dwarfism originally considered to have this syndrome. On re-evaluation of their clinical and radiographic features, only one of them had the typical features of the Grebe chondrodysplasia, whereas the other two appear to have clearly distinct, previously unreported skeletal dysplasias. These patients illustrate the heterogeneity that exists among the nonlethal forms of severe short-limbed dwarfism.

Adult↗
PubMed1977

Grebe chondrodysplasia and similar forms of severe short-limbed dwarfism.

We have studied three patients with severe short-limbed dwarfism, only one of whom had the typical features of Grebe disease, whereas the other two had clearly distinct previously unreported skeletal dysplasias. Unlike the patients with Grebe disease, the latter two patients had involvement of the spine and particularly short humeri. The malformations of the hands and lower limbs were different in each of the three patients.

Adult↗
PubMed1976

Mitochondrial and nuclear glutamate dehydrogenases in Chinese hamster ovary cells in culture.

Nuclear glutamate dehydrogenase (EC 1.4.1.3) activity has been demonstrated in Chinese hamster ovary cells. Some characteristics of this enzyme have been examined and compared with those of the mitochondrial glutamate dehydrogenase from the same source. Differences were detected in the extent of the activation by inorganic phosphate, in the pH versus activity curves, in the affinity of the two enzymes for the cofactor NAD+ and in the electrophosretic mobility. A different rate of decay of the two enzymes has been observed in cells grown in the presence of chloramphenicol. Immunological studies show that, as in ox liver, the nuclear enzyme has specific antigenic determinants besides those in common with mitochondrial glutamate dehydrogenase. Finally, experiments of thermal inactivation indicate a higher stability of the mitochondrial enzyme.

Cell Nucleus↗
PubMed1976

Mosaicism for sulfoiduronate sulfatase deficiency in carriers of Hunter's syndrome.

Using an assay for sulfoiduronate sulfatase based on the degradation of 35S mucopolysaccharides in a cell-free system, two clonal populations have been demonstrated in fibroblasts of heterozygotes for Hunter's syndrome. The locus responsible for sulfoiduronate sulfatase deficiency in this X-linked mucopolysaccharidosis is therefore subjected to dosage compensation in females.

Clone Cells↗
PubMed1976

Human alpha-fucosidase. Purification and properties.

Human placental alpha-fucosidase (EC 3.2.1.51) has been extensively purified and partially characterized with respect to kinetic and structured properties. Although the enzyme seems to be separated by DEAE-cellulose chromatography in two forms which differ in their molecular weight and thermostability, an interconversion between the two forms takes place during storage and/or electrofocusing so that the same peaks of activity, revealed by the latter technique, are found before and after DEAE-cellulose chrome. The heterogeneous peaks of activity revealed by isoelectrofocusing show a reproducible pattern in the different tissues examined, except in serum where their pI values are consistently more acidic.

Brain↗
PubMed1976

Human alpha-fucosidase. Single residual enzymatic form in fucosidosis.

Four major forms of alpha-fucosidase (EC 3.2.1.51) activity were separated by isoelectrofocusing from sera of normal control individuals. All forms shifted towards less acidic pI values after neuraminidase treatment. In two patients affected with fucosidosis, only a single major acidic peak was observed and this was affected to a lesser degree by neuraminidase treatment. The kinetics of heat inactivation of the residual activity found in these two patients showed two decay rates while the controls showed only one rate. These data are considered in relation to the hypothesis of the existence of interconvertible thermolabile and thermostable forms of the enzyme which has been discussed in the preceeding paper. The residual alpha-fucosidase found in patients could be structurally altered so that its ability to form the thermostable higher molecular weight aggregates is impaired.

Adolescent↗
PubMed1976

Hair root versus red cell individual phenotype in Sardinian heterozygotes for G6PD deficiency (Mediterranean type).

G6PD activity was assayed in 20 Sardinian heterozygotes for G6PD deficiency and related to that of LDH and MDH. One of these heterozygotes showed a deficient phenotype in all her follicles, while the remaining 19 had different proportions of deficient, intermediate, and normal follicles. This is in accordance with a previous estimate. Because of the broad fiducial limits at the 5% level and because of some developmental considerations, this value cannot be interpreted as indicative of the number of primordial cells for scalp epidermis at the time of X-chromosome inactivation, as previously stated. The assay of single hair follicles is, however, a very valuable tool for establishing the role of cell selection in the same or in a different tissue, like peripheral blood.

Erythrocytes↗
PubMed1975

Stability of X chromosomal inactivation in human somatic cells transformed by SV-40.

Clones of fibroblasts from a G6PD A heterozygote transformed with SV-40 did not express the G6PD silent allele in the transformed heteroploid cultures. In addition, transformed fibroblasts from a woman heterozygous for both G6PD A and HGPRT deficiency, subjected to selective pressure, did not reveal a single cell expressing either silent allele. Since the incidence of sex chromatin was significantly lower in these cells after transformation, it is likely that the loss of sex chromatin reflects the loss of the inactive X-chromosome at an early stage following transformation.

Aneuploidy↗