Steady-state kinetic studies of glutathione reductase

The steady-state kinetic studies of yeast glutathione reductase, performed when [GSSG] = 10[NADPH] in the assay mixture, show that at concentrations of GSSG under 450 microM the enzymatic mechanism pathway is ping-pong. Furthermore, in the case of higher values, the enzymatic kinetics follows a sequential pathway. However when the glutathione reductase reaction passes to the ping-pong mechanism, the inhibition effect by excess of NADPH is stronger than when the reaction takes place over the sequential mechanism.     

Plasma transferrin phenotype and gene frequencies in the population of Rome (Italy)

Summary Frequencies of transferrin phenotypes and genes were determined in a sample of 319 randomly selected subjects from the population of Rome. Disc electrophoresis on acrylamide gel columns was adopted for the phenotype identification. A statistical analysis on these and all the data so far collected in other areas of the world would suggest that a high degree of homogeneity is present among white populations, while a certain degree of heterogeneity exists among coloured populations.     

Human erythrocyte hexokinases are immunologically related

Human erythrocytes contain three major hexokinase isoenzymes eluted by DE-52 chromatography between hexokinase type I and type II. Cross-reactivities of these isoenzymes were studied by means of a monospecific rabbit antibody against purified human placenta hexokinase type I. It was shown that the three hexokinase isoenzymes were immunologically related, supporting the concept of a postsynthetic mechanism(s) as their origin.     

Essential oil composition and total metabolite content of a chemotype of Ajuga reptans L. (Lamiaceae) collected in Central Italy

In this work, an interesting application of phytochemistry for ethnopharmacological purposes was reported. In particular, the total phytochemical analysis of a single sample of Ajuga reptans L. (Lamiaceae) collected in Central Italy was carried out in order to provide a rationale for the use of this plant in folk medicine. This analysis was conducted on the volatile oil fraction by gas chromatography–mass spectroscopy (GC-MS) and on the polar one by means of classical column chromatography and nuclear magnetic resonance and MS. Thirty-nine volatile components were identified in the essential oil whereas 32 compounds were identified in the polar fraction. All of these are known to exert several beneficial medicinal activities and no potentially toxic compounds were identified such as the neo-clerodane diterpenoids, commonly evidenced in the entire genus. This study could provide a phytochemical rationale for the possible ethnopharmacological use of this specific species.     

Assessing the essentiality of the decaprenyl‐phospho‐d‐arabinofuranose pathway in Mycobacterium tuberculosis using conditional mutants

In Mycobacterium tuberculosis the decaprenyl‐phospho‐d ‐arabinofuranose (DPA) pathway is a validated target for the drugs ethambutol and benzothiazinones. To identify other potential drug targets in the pathway, we generated conditional knock‐down mutants of each gene involved using the TET‐PIP OFF system. dprE1, dprE2, ubiA, prsA, rv2361c, tkt and rpiB were confirmed to be essential under non‐permissive conditions, whereas rv3807c was not required for survival. In the most vulnerable group, DprE1‐depleted cells died faster in vitro and intracellularly than those lacking UbiA and PrsA. Downregulation of DprE1 and UbiA resulted in similar phenotypes, namely swelling of the bacteria, cell wall damage and lysis as observed at the single cell level, by real time microscopy and electron microscopy. By contrast, depletion of PrsA led to cell elongation and implosion, which was suggestive of a more pleiotropic effect. Drug sensitivity assays with known DPA‐inhibitors supported the use of conditional knock‐down strains for target‐based whole‐cell screens. Together, our work provides strong evidence for the vulnerability of all but one of the enzymes in the DPA pathway and generates valuable tools for the identification of lead compounds targeting the different biosynthetic steps. PrsA, phosphoribosyl‐pyrophosphate synthetase, appears to be a particularly attractive new target for drug discovery.     

Sugar levels in Charmat sparkling wines can affect the quality and resveratrol levels

Sparkling wines contain CO(2) obtained through a second fermentation by natural processes (Charmat method); they may be prepared with variable final sugar concentrations, resulting in physicochemical compositions and phenolic profiles different to those obtained with other natural methods. The purpose of this study was to verify the influence of sweetness on enological parameters, trans-resveratrol and trans-piceid levels, antioxidant capacity (power of scavenger the radical DPPH(?) (1,1-diphenyl-2-picrylhydrazyl) and mimetic enzymatic activities of superoxide dismutase (SOD-like) and catalase (CAT-like) assays, and β-glucosidase activities on Charmat sparkling wines. The interaction of polyphenol levels and sweetness was observed. Levels of trans-piceid and trans-resveratrol showed a decrease in function of glucose concentration up to 40 g/l. All samples showed antioxidant capacity and β-glucosidase activity was stable even in the presence of sugar. A positive correlation between SOD-like and DPPH(?) was observed. This work shows an approach able to clarify important aspects for the wine industry with regard to world-wide consumer demand for sweetened products.