Formation of the tight-binding inhibitor, 3-ketoarabinitol-1,5-bisphosphate by ribulose-1,5-bisphosphate carboxylase/oxygenase is O2-dependent

Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) (EC 4.1.1.39) not only catalyzes carboxylation and oxygenation of ribulose-1,5-bisphosphate (RuBP), but it can also act either as an epimerase or isomerase converting RuBP into xylulose-1,5-bisphosphate (XuBP) or 3-ketoarabinitol-1,5-bisphosphate (KABP), respectively, a process called misfire. XuBP is formed as a result of misprotonation at C3 of the RuBP-enediol. It is released from Rubisco active sites and accumulates in the reaction mixture. Increasing the amounts of CO₂ or O₂ decreases XuBP production. However, KABP synthesis, which has been proposed to be only a product due to C2 misprotonation of the RuBP-endiol, is dependent upon the presence of O₂. KABP remains tightly bound to Rubisco active sites after its formation, causing the loss of Rubisco activity (fallover). The results suggest that the non-stabilized form of the peroxy-intermediate in the oxygenase reaction can be converted in a backreaction to KABP and molecular oxygen. The stabilization of the peroxy-intermediate due to the presence of Mn²⁺ instead of Mg²⁺ eliminates the formation of KABP.     

Abiotic Stress Tolerance： From Gene Discovery in Model Organisms to Crop Improvement

Productive and sustainable agriculture necessitates growing plants in sub-optimal environments with less input of precious resources such as fresh water. For a better understanding and rapid improvement of abiotic stress tolerance, it is important to link physiological and biochemical work to molecular studies in genetically tractable model organisms. With the use of several technologies for the discovery of stress tolerance genes and their appropriate alleles, transgenic approaches to improving stress tolerance in crops remarkably parallels breeding principles with a greatly expanded germplasm base and will succeed eventually.     

Anaerobic degradation of papermill sludge in a two-phase digester containing rumen microorganisms and colonized polyurethane foam

Summary The use of reticulated polyurethane foam as a support material for the immobilization of methanogenic associations and its application to the anaerobic treatment of fine particulate solid wastes was investigated. The colonization of polyurethane support particles in a continuous upflow reactor fed on a mixture of acetate, propionate and butyrate, was both rapid and dense. The combination of rumen microorganisms and colonized support particles in a two-phase digester resulted in an efficient anaerobic decomposition of papermill sludge.     

Effects of common atopy-associated amino acid substitutions in the IL-4 receptor alpha chain on IL-4 induced phenotypes

The human IL-4 receptor alpha chain gene (IL4R) is highly polymorphic and controversial reports have been published with respect to the association of different single nucleotide polymorphisms (SNPs) with atopy markers. Here we analyzed the functional and associational relevance of common IL4R coding SNPs. Transfection of B cell lines expressing the IL-4R variant V75+R576 did not result in enhanced IL-4 induced CD23 expression compared to cell lines expressing the wild type IL-4R alpha chain. Transfection of the IL-4R variant P503 into a murine T cell line did not influence IL-4 induced T-cell proliferation compared to wild type constructs. Analysis of six IL4R coding SNPs (I75V, E400A, C431R, S436L, S503P, Q576R) and common haplotypes (frequency 0.05%) in blood donors (n=300) did not indicate a significant association with elevated serum IgE level. Moreover, the most informative IL4R coding SNPs (I75V, C431R, Q576R) and related two- and three-point haplotypes (frequency 0.05%) were analyzed in a second, extended group of blood donors (n=689). Again, no significant association with elevated serum IgE was detectable. We conclude that common coding SNPs in the IL4R gene are unlikely to contribute significantly to increased IgE levels and variations outside the coding region may influence atopy susceptibility.