Kinetic properties of a L-cysteine desulfhydrase-deficient mutant in the enzymatic formation of L-cysteine from D,L-ATC

Summary A mutant strain lacking in activity of L-cysteine desulfhydrase, a L-cysteine-decomposing enzyme, was screened after UV-treatment ofPseudomonas sp. CU6. The properties of the two strains, original and mutant, were compared on the basis of parameter values estimated from kinetic simulations of the enzymatic formation of L-cysteine from D,L-ATC. Both strains suffered from product inhibition, though inhibition was less for the mutant strain.     

Tolerance of <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> K35 to lignocellulose-derived inhibitory compounds

The hydrolysis which converts polysaccharides to the fermentable sugars for yeast’s lingocellulosic ethanol production also generates byproducts which inhibit the ethanol production. To investigate the extent to which inhibitory compounds affect yeast’s growth and ethanol production, fermentations by Saccharomyces cerevisiae K35 were investigated in various concentrations of acetic acid, furfural, 5-hydroxymethylfurfural (5-HMF), syringaldehyde, and coumaric acid. Fermentation in hydrolysates from yellow poplar and waste wood was also studied. After 24 h, S. cerevisiae K35 produced close to theoretically predicted ethanol yields in all the concentrations of acetic acid tested (1 ∼ 10 g/L). Both furans and phenolics inhibited cell growth and ethanol production. Ethanol yield, however, was unaffected, even at high concentrations, except in the cases of 5 g/L of syringaldehyde and coumaric acid. Although hydrolysates contain various toxic compounds, in their presence, S. Cerevisiae K35 consumed close to all the available glucose and yielded more ethanol than theoretically predicted. S. Cerevisiae K35 was demonstrated to have high tolerance to inhibitory compounds and not to need any detoxification for ethanol production from hydrolysates.     

Metformin sensitizes insulin signaling through AMPK-mediated PTEN down-regulation in preadipocyte 3T3-L1 cells

Insulin resistance is the primary cause responsible for type 2 diabetes. Phosphatase and tensin homolog (PTEN) plays a negative role in insulin signaling and its inhibition improves insulin sensitivity. Metformin is a widely used insulin-sensitizing drug; however, the mechanism by which metformin acts is poorly understood. To gain insight into the role of PTEN, we examined the effect of metformin on PTEN expression. Metformin suppressed the expression of PTEN in an AMP-activated protein kinase (AMPK)-dependent manner in preadipocyte 3T3-L1 cells. Knock-down of PTEN potentiated the increase in insulin-mediated phosphorylation of Akt/ERK. Metformin also increased the phosphorylation of c-Jun N-terminal kinase (JNK)-c-Jun and mammalian target of rapamycin (mTOR)-p70S6 kinase pathways. Both pharmacologic inhibition and knock-down of AMPK blocked metformin-induced phosphorylation of JNK and mTOR. Knock-down of AMPK recovered the metformin-induced PTEN down-regulation, suggesting the involvement of AMPK in PTEN regulation. PTEN promoter activity was suppressed by metformin and inhibition of mTOR and JNK by pharmacologic inhibitors blocked metformin-induced PTEN promoter activity suppression. These findings provide evidence for a novel role of AMPK on PTEN expression and thus suggest a possible mechanism by which metformin may contribute to its beneficial effects on insulin signaling.     

Replacement of Ca by Ni in a Perovskite Titanate to Yield a Novel Perovskite Exsolution Architecture for Oxygen‐Evolution Reactions

For efficient catalysis and electrocatalysis well‐designed, high‐surface‐area support architectures covered with highly dispersed metal nanoparticles with good catalyst‐support interactions are required. In situ grown Ni nanoparticles on perovskites have been recently reported to enhance catalytic activities in high‐temperature systems such as solid oxide cells (SOCs). However, the micrometer‐scale primary particles prepared by conventional solid‐state reactions have limited surface area and tend to retain much of the active catalytic element within the bulk, limiting efficacy of such exsolution processes in low‐temperature systems. Here, a new, highly efficient, solvothermal route is demonstrated to exsolution from smaller scale primary particles. Furthermore, unlike previous reports of B‐site exsolution, it seems that the metal nanoparticles are exsolved from the A‐site of these perovskites. The catalysts show large active site areas and strong metal‐support interaction (SMSI), leading to ≈26% higher geometric activity (25 times higher mass activity with 1.4 V of E_on‐set) and stability for oxygen‐evolution reaction (OER) with only 0.72 µg base metal contents compared to typical 20 wt% Ni/C and even commercial 20 wt% Ir/C. The findings obtained here demonstrate the potential design and development of heterogeneous catalysts in various low‐temperature electrochemical systems including alkaline fuel cells and metal–air batteries.     

A putative role of Drep1 in apoptotic DNA fragmentation system in fly is mediated by direct interaction with Drep2 and Drep4

DNA fragmentation is common phenomenon for apoptotic cell death. DNA fragmentation factor, called DFF40 (CAD: mouse homologue), is a main nuclease for apoptotic DNA fragmentation. Nuclease activity of DFF40 is normally inhibited by DFF45 by tight interaction via CIDE domain without apoptotic stimuli. Once effector caspase is activated during apoptosis signaling, it cleave DFF45, allowing DFF40 to enter the nucleus and cleave chromosomal DNA. Unlike mammalian system, apoptotic DNA fragmentation in the fly might be controlled by four DFF-related proteins, known as Drep1, Drep2, Drep3 and Drep4. Although the function of Drep1 and Drep4 is well known as DFF45 and DFF40 homologues, respectively, the function of Drep2 and Drep3 is still unclear. DFF-related proteins contain a conserved CIDE domain of ~90 amino acid residues that is involved in protein–protein interaction. Here, we showed that Drep1 directly bind to Drep2 as well as Drep4 via CIDE domain. In addition, we found that the interaction of Drep2 and Drep4 to Drep1 was not competitive indicating that Drep2 and Drep4 bind different place of Drep1. All together, we suggest that Drep1 might be involved in apoptotic DNA fragmentation of fly system by direct interaction with Drep2 as well as Drep4.     

Identification and characterization of proteins isolated from microvesicles derived from human lung cancer pleural effusions

Microvesicles (MVs, also known as exosomes, ectosomes, microparticles) are released by various cancer cells, including lung, colorectal, and prostate carcinoma cells. MVs released from tumor cells and other sources accumulate in the circulation and in pleural effusion. Although recent studies have shown that MVs play multiple roles in tumor progression, the potential pathological roles of MV in pleural effusion, and their protein composition, are still unknown. In this study, we report the first global proteomic analysis of highly purified MVs derived from human nonsmall cell lung cancer (NSCLC) pleural effusion. Using nano‐LC–MS/MS following 1D SDS‐PAGE separation, we identified a total of 912 MV proteins with high confidence. Three independent experiments on three patients showed that MV proteins from PE were distinct from MV obtained from other malignancies. Bioinformatics analyses of the MS data identified pathologically relevant proteins and potential diagnostic makers for NSCLC, including lung‐enriched surface antigens and proteins related to epidermal growth factor receptor signaling. These findings provide new insight into the diverse functions of MVs in cancer progression and will aid in the development of novel diagnostic tools for NSCLC.