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The present communication describes the properties of isocitrate dehydrogenase in crude extracts from the unicellular Anacystis nidulans and from heterocysts and vegetative cells of Nostoc muscorum and Anabaena cylindrica. The activity levels of this enzyme are much higher in heterocysts than in vegetative cells of N. muscorum and A. cylindrica. Isocitrate dehydrogenase is virtually inactive in vegetative cells of A. cylindrica. The enzyme is negatively regulated by the reduction charge and scarcely affected by oxoglutarate in the three cyanobacteria. The inhibition by ATP and ADP is competitive with respect to isocitrate and NADP+ in A. cylindrica and N. muscorum and noncompetitive in A. nidulans. Isocitrate dehydrogenase from the three cyanobacteria seems to be a hysteretic enzyme. All the experimental data suggest that the major physiological role of isocitrate and the isocitrate dehydrogenase in heterocysts is not to generate reducing equivalents for N2-fixation. Oxoglutarate formed by the enzyme reaction is likely required for the biosynthesis of glutamate inside the heterocysts. Thioredoxin preparations from spinach chloroplasts or from A. cylindrica activate isocitrate dehydrogenase from either heterocysts or vegetative cells of A. cylindrica. Activation is completed within seconds and requires dithiothreitol besides thioredoxin. The thioredoxin preparation which activates isocitrate dehydrogenase also activates NADP+-dependent malate dehydrogenase from spinach chloroplasts or heterocysts of A. cylindrica. Isocitrate dehydrogenase from A. cylindrica is deactivated by oxidized glutathione. It is speculated that isocitrate dehydrogenase and thioredoxin play a role in the differentiation of vegetative cells to heterocysts.

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Purpose Greenhouse gas (GHG) emissions have been identified as one of Unilever's priority environmental impact themes: this assessment was therefore conducted to help the Knorr brand measure and understand the GHG emissions related to its product portfolio, identify opportunities to manage GHG emissions in the Unilever-owned operations (manufacture) and influence managed reductions elsewhere in the Knorr product lifecycles, and assess the impact of the brand's innovation and portfolio strategies on its GHG footprint. Methods A bottom-up product-based life cycle assessment (LCA) approach was considered impractical to assess Knorr's portfolio's complexity. Thus, a meta-product-based accounting LCA approach was followed (Milà i Canals et al. 2009). Up to 16 product types or "meta-products" were assessed in each geographical region, with a total of 36 meta-products assessed globally. Then, the Knorr GHG footprint was derived by multiplying the impacts calculated per tonne of each product type with the sales volumes in 2007. Data for ingredients and processing technologies were gathered from the literature and suppliers; data from Knorr factories were used for the manufacturing stage. The variability in ingredients' production and processing and in manufacture was factored in and propagated through the calculations to assess the robustness of the results. Results The profiles of different meta-products within a product group (e.g. dry soups) follow similar patterns in terms of absolute GHG per tonne and distribution of such emissions along the life cycle. Variations are observed due to recipe composition and electricity mixes in the different regions. The range of variability around absolute results is significant and varies between meta-products. Aggregating the results for individual meta-products with their production volumes, the global Knorr brand GHG footprint in 2007 was estimated to be in the region of 3-5 million tonnes CO 2 e/ annum (95% confidence interval). In spite of the significant variability ranges found, the results are useful for target setting and identification of opportunities for improvement. Conclusions This is the world's first life cycle GHG assessment at brand's product portfolio level. The metaproduct approach simultaneously allows for the assessment and comparison of individual product types as well as for the estimation of a brand's total GHG. The variability assessment enhanced robustness of the results by identifying a confidence range; given the complexity of the studied supply chains and the current data quality translated in wide confidence ranges, single number on-pack carbon labels seem questionable and not robust enough to inform consumers.

Flavodoxin and ferredoxin become reduced in Escherichia coli cells by oxidoreductase reactions which use pyruvate and NADPH as electron donor substrates. The two enzymes, which are minor proteins of this organism, were measured through the reduced flavodoxin‐dependent activation of pyruvate formate‐lyase. The NADPH‐dependent enzyme, obtained homogeneously through Procion‐red affinity chromatography, was identified as the flavoprotein ‘component R’ described previously by Fujii and Huennekens [J. Biol. Chem. 249, 6745–6753 (1974)]. The pyruvate‐dependent enzyme was identified as CoA‐acetylating pyruvate; flavodoxin (ferredoxin) oxidoreductase. Its catalytic properties in the forward. reverse, and the 14CO2‐pyruvate exchange reaction are reported. The dihydro form of flavodoxin was characterized as the particular species involved in the activation of pyruvate formate‐lyase. The activation process still occurs with 70% of maximal efficiency when the ratio [NADPH]/([NADP] + [NADPH]) is fixed at the intracellular ‘anabolic reduction charge’ value of 0.45, in conjunction with the NADPH‐dependent enzyme. The [2Fe‐2S] ferredoxin, though being readily used as electron acceptor of both oxidoreductases and having a redox potential similar to flavodoxin, proved incompetent in mediating the activation of pyruvate formate‐lyase.