ABSTRACT
Hyper-osmotic stress is one of the key factors that decrease the efficiency of biological succinic acid production. To increase the osmotic stress tolerance of succinate-producing Escherichia coli, we studied the influence of IrrE, an exogenous global regulator, on cell osmotic stress resistance. Fermentation results showed that cell growth and succinic acid production by the recombinant increased under different Na+ concentrations. Meanwhile, the maximum dry cell mass, glucose consumption and succinic acid concentration increased 15.6%, 22% and 23%, respectively, when fermented in a 5-L bioreactor. Expressing IrrE improved cell resistance to hyper-osmotic stress. Further comparison of intracellular osmoprotectants (trehalose and glycerol) concentrations showed that trehalose and glycerol concentrations in the recombinant increased. This suggested that introduction of IrrE could enhance intracellular osmoprotectants accumulation which conferred cell with improved resistance to osmotic stress.
ABSTRACT
Dysfunction in tyrosine kinase activity disrupts the nor-mal control of cellular phosphorylation signaling pathways,which plays a vital role in genesis and development of various tumors, and makes tyrosine kinases a class of targets of many anti-tumor drugs. Currently most approved tyrosine kinase inhibitors ( TKIs) are based on irreversible binding mechanisms, making them poorly selective, not potent or sustained enough regarding pharmacological effects and prone to triggering resistance. In the past decade, much progress has been made in the development of a new class of TKIs which irreversibly inhibit their target proteins via the formation of covalent bonds, overcoming the drawbacks of irreversible TKIs. Several irreversible TKIs have entered markets or clinical research phases. This review is to summarize the structural, pharmacological and medicinal chemical properties of investigational and marketed irreversible TKIs as well as their re-cent developments.