Modeling the Role of Negative Cooperativity in Metabolic Regulation and Homeostasis

A significant proportion of enzymes display cooperativity in binding ligand molecules, and such effects have an important impact on metabolic regulation. This is easiest to understand in the case of positive cooperativity. Sharp responses to changes in metabolite concentrations can allow organisms to better respond to environmental changes and maintain metabolic homeostasis. However, despite the fact that negative cooperativity is almost as common as positive, it has been harder to imagine what advantages it provides. Here we use computational models to explore the utility of negative cooperativity in one particular context: that of an inhibitor binding to an enzyme. We identify several factors which may contribute, and show that acting together they can make negative cooperativity advantageous.     

α‐ketoglutarate delays age‐related fertility decline in mammals

The fecundity reduction with aging is referred as the reproductive aging which comes earlier than that of chronological aging. Since humans have postponed their childbearing age, to prolong the reproductive age becomes urgent agenda for reproductive biologists. In the current study, we examined the potential associations of α‐ketoglutarate (α‐KG) and reproductive aging in mammals including mice, swine, and humans. There is a clear tendency of reduced α‐KG level with aging in the follicle fluids of human. To explore the mechanisms, mice were selected as the convenient animal model. It is observed that a long term of α‐KG administration preserves the ovarian function, the quality and quantity of oocytes as well as the telomere maintaining system in mice. α‐KG suppresses ATP synthase and alterations of the energy metabolism trigger the nutritional sensors to down‐regulate mTOR pathway. These events not only benefit the general aging process but also maintain ovarian function and delay the reproductive decline. Considering the safety of the α‐KG as a naturally occurring molecule in energy metabolism, its utility in reproduction of large mammals including humans deserves further investigation.     

Clinical significance of platelet alloantibodies detected in immunofluorescence test (neonatal alloimmune thrombocytopenia and post-transfusion purpura)

Three cases of neonatal alloimmune thrombocytopenia and one patient with post-transfusion purpura could be diagnosed only by introducing the platelet immunofluorescence test. Thrombocytopenia was caused by anti-PlA1 platelet alloantibodies detected neither in the agglutination nor by the complement fixation test.     

The evolution of Nyctereutes (Carnivora: Canidae) in the Nihewan Basin,Hebei, northern China

The occurrence of Nyctereutes during the Plio-Pleistocene has long been reported in northern China, with the highest abundance in the Nihewan Basin. However, due to site dispersal, the coexistence of different taxa, and lack of a precise stratigraphic constraint, the evolutionary process of this genus remains enigmatic. In this study, we re-examined the available Nyctereutes materials recovered from the Nihewan Basin housed in IVPP and Tianjin Natural History Museum, in addition to a newly recovered specimen from our latest excavation. Furthermore, we compared these materials with Nyctereutes fossils recovered from the Pleistocene Zhoukoudian sites near Beijing and the extant species N. procyonoides. Our analysis of the upper molar morphometry reveals the variations in size and dietary characteristics within different species of Nyctereutes during the late Plio-Pleistocene. The examination of molars indicates an increase in the size of Nyctereutes sinensis compared to early Pliocene N. tingi as well as changes in the molar teeth morphology. Subsequently, changes in diet or environmental factors possibly caused the decrease of body size in the late Pleistocene. We also estimate an age constraint for the fossils of N. sinensis from the Xiashagou section by relocating Licent's localities and referring of updated magnetostratigraphic data.     

Enzymes of cyclic nucleotide degradation in eye tissues during experimental ocular herpes

Activity of phosphodiesterases disintegrating cAMP and cGMP in the cornea, sclera and ciliary body was investigated in health and in different stages of experimental herpetic keratitis. The problems concerning the role of the cyclase system in the pathogenesis of herpetic keratitis and the possibility of applying some of the drugs to the disease treatment are discussed.     

Engineering of Thermomyces lanuginosus lipase Lip: creation of novel biocatalyst for efficient biosynthesis of chiral intermediate of Pregabalin

Efficient and highly enantioselective hydrolysis of 2-carboxyethyl-3-cyano-5-methylhexanoic acid ethyl ester (CNDE) is the most crucial step in chemoenzymatic synthesis of Pregabalin. By using site-saturation mutagenesis and high-throughput screening techniques, lipase Lip from Thermomyces lanuginosus DSM 10635 was engineered to improve its activity towards CNDE. The triple mutant, S88T/A99N/V116D exhibited a 60-fold improvement in specific activity for CNDE (2.35 U/mg) over the wild-type Lip (0.039 U/mg). Modeling and docking studies demonstrated that the mutant could more effectively stabilize oxygen anions in transition states and the lid of Lip in the open conformation. Additionally, the kinetic resolution of CNDE catalyzed by Escherichia coli cell overexpressing S88T/A99N/V116D mutant afforded (3S)-2-carboxyethyl-3-cyano-5-methylhexanoic acid in 42.4 % conversion and 98 % ee within 20 h with a substrate loading of 1 M (255 g/l). These results demonstrated that a novel and promising biocatalyst was created for efficient chemoenzymatic manufacturing of Pregabalin.