Molecular characterization of porphyrias in Italy: a diagnostic flow-chart.

The porphyrias are disorders associated with inherited or acquired enzyme deficiencies in the heme biosynthetic pathway. The differential diagnosis is often difficult since the phenotype is very similar in some forms and the biochemical tests are not commonly available. Here we provide an update on the molecular diagnosis of porphyrias in Italy and a flow-chart to facilitate the identification of mutations in heme biosynthetic genes. The molecular analysis has allowed us to identify the molecular defect underlying the disease in 66 probands with different porphyrias [acute intermittent porphyria (AIP), variegate porphyria (VP), porphyria cutanea tarda (PCT), erythropoietic protoporphyria (EPP)]. No Italian patients with defects in coproporphyrinogen oxidise (CPOX) gene, responsible for hereditary coproporphyria (HCP), have been detected. The molecular characterization has been extended to 115 relatives with the identification of 55 asymptomatic mutation carriers and 60 normal subjects. We have so far identified 50 different mutations among 4 genes associated with the most common porphyrias showing a high molecular heterogeneity: 22 in the hydroxymethylbilane synthase (HMBS) gene (AIP), 7 in the protoporphyrinogen oxidase (PPOX) gene (VP), 16 in the uroporphyrinogen decarboxylase (UROD) gene (PCT) and 5 in the ferrochelatase (FECH) gene (EPP). Among the 50 molecular defects, 29 seem to be restricted to the Italian population.     

Preparation of a chiral ferrocenyl derivative containing a biphenyl unit via nickel-mediated homocoupling

Ferrocenyl derivative 2, which possesses a biphenyl unit, was prepared by nickel(0)-mediated homocoupling of a chiral ferrocenyloxazoline. Compound 2 exists as an equilibrium mixture of two diastereomers, in a ratio dependent on temperature and solvent, due to the partially hindered rotation around biaryl bond. Upon complexation with Cu(I) or Zn(II), complete fixation of the stereogenic axis was obtained and a single stable atropoisomer was formed, whose absolute configuration was assigned on the basis of its NOESY spectrum. The 2-Cu(I) complex was used as catalyst in the cyclopropanation of styrene.     

The yeast multicopper oxidase Fet3p and the iron permease Ftr1p physically interact

High affinity iron uptake in yeast is carried out by a multicomponent system formed by the ferroxidase Fet3p and the iron permease Ftr1p. The currently accepted model predicts that Fet3p and Ftr1p are functionally associated, however, a structural interaction between these two proteins has not been proven yet. The methylotrophic yeast Pichia pastoris has been used to perform cross-linking studies aimed to demonstrate the existence of a Fet3p-Ftr1p complex. Cross-linking of membrane suspensions with the membrane-impermeable reagents DTSSP and BS(3) has evidenced the presence of a high molecular weight band with Fet3p oxidase activity. This band has been purified and subjected to N-terminal sequence analysis. Two sequences were found in the cross-linked species, one of which could be assigned to Fet3p and the other to Ftr1p. This is the first experimental demonstration that Fet3p and Ftr1p are physically associated.     

Metabolic control analysis reveals an important role for diacylglycerol acyltransferase in olive but not in oil palm lipid accumulation

We applied metabolic control analysis to the Kennedy pathway for triacylglycerol formation in tissue cultures from the important oil crops, olive (Olea europaea L.) and oil palm (Elaeis guineensis Jacq.). When microsomal fractions were incubated at 30 degrees C rather than 20 degrees C, there was an increase in triacylglycerol labelling. This increase was accompanied by a build up of diacylglycerol (DAG) radioactivity in olive but not in oil palm, suggesting that the activity of DAG acyltransferase (DAGAT) was becoming limiting in olive. We used 2-bromooctanoate as a specific inhibitor of DAGAT and showed that the enzyme had a flux control coefficient under the experimental conditions of 0.74 in olive but only 0.12 in oil palm. These data revealed important differences in the regulation of lipid biosynthesis in cultures from different plants and suggest that changes in the endogenous activity of DAGAT is unlikely to affect oil accumulation in oil palm crops.     

The role of latitudinal,genetic and temperature variation in the induction of diapause of Papilio glaucus (Lepidoptera: Papilionidae)

A key adaptation in insects for dealing with variable environmental conditions is the ability to diapause. The tiger swallowtail butterflies, Papilio glaucus and P. canadensis are ideal species to explore the genetic causes and population genetic consequences of diapause because divergence in this trait is believed to be a salient factor in maintaining a hybrid zone between these species. Yet little is known about the factors that influence diapause induction in this system. Here we explored how spatial (latitudinal), environmental (temperature) and genetic (hybridization) factors affect diapause induction in this system. Specifically, a series of growth chamber experiments using wild caught individuals from across the eastern United States were performed to: (1) evaluate how critical photoperiod varies with latitude, (2) isolate the stage in which induction occurs, (3) test whether changes in temperature affected rates of diapause induction, and (4) explore how the incidence of diapause is affected in hybrid offspring. We find that induction occurs in the larval stage, is not sensitive to a relatively broad range of temperatures, appears to have a complex genetic basis (i.e., is not simply a dominant trait following a Mendelian inheritance pattern) and that the critical photoperiod increases by 0.4 h with each increasing degree in latitude. This work deepens our understanding of how spatial, environmental and genetic variation influences a key seasonal adaptation (diapause induction) in a well‐developed ecological model system and will make possible future studies that explore how climatic variation affects the population dynamics and genetics of this system.     

The Foxo1-Inducible Transcriptional Repressor Zfp125 Causes Hepatic Steatosis and Hypercholesterolemia

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Consumption of NADPH for 2-HG Synthesis Increases Pentose Phosphate Pathway Flux and Sensitizes Cells to Oxidative Stress

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A simple mechanism decreasing free metabolite pool size in static spatial channelling

We propose a simple mechanism which enables decrease of the free pool of channelled metabolite in static spatial channelling, when the concentration of the enzyme consuming the channelled metabolite is greater than the concentration of the enzyme producing this metabolite. Spatial channelling occurs between two enzymes when the common metabolite is released to a small space between these enzymes and does not form a ternary covalent complex with them, as is the case in covalent (dynamic or static) channelling. The mechanism proposed is qualitatively independent of rate constants, metabolite concentrations as well as other kinetic properties and is quantitatively significant for all physiologically relevant conditions. Calculations show that the free metabolite pool must decrease, when the concentration of the enzyme consuming the channelled metabolite is greater than the enzyme producing it. This mechanism is much more effective than increase in the concentration (or rate constant) of the enzyme consuming the metabolite in the absence of spatial channelling.