A cyclopeptidic suicide substrate preferentially inactivates urokinase-type plasminogen activator.

c[Arg-aB-(CH2+SCH3 phi)-Gly4] was designed and studied as a mechanism-based inactivator (suicide substrate) for plasminogen activators (u-PA and t-PA) and plasmin. This compound inhibited u-PA and fulfills criteria expected for the involvement of an enzyme-activated inhibitor: first-order and irreversible process, saturation kinetics, protection by substrate. The limiting first-order rate constant kinact and the apparent enzyme-inhibitor dissociation constant KI were 0.021 s-1 and 9 microM, respectively at pH 7.5 and 25 degrees C. The activation of plasminogen by u-PA is compromised after this enzyme has been treated by the reagent. Plasmin and t-PA were inactivated 40- and 2330-fold less efficiently than u-PA, respectively.     

Acyloxybenzyl halides, inhibitors of elastases

3-Benzyl-6-chloromethyl-3,4-dihydrocoumarin inhibits human leucocyte elastase (HLE) and porcine pancreatic elastase (PPE) through a mechanism-based process characterized by the following apparent enzyme-inhibitor dissociation constants, Ki, and limiting inactivation rate constants k2: 200 microM (HLE), 69 microM (PPE) and 5.10(-2) s-1 (HLE), 17.7.10(-2) s-1 (PPE) at pH 8.0, 37 degrees C. Bis(4-acyloxyphenyl)methane derivatives with a benzylic halogen as potential leaving group have also been synthesized and studied. They transiently inactivate PPE and HLE through the formation of an acyl-enzyme.     

Systemic GDF11 stimulates the secretion of adiponectin and induces a calorie restriction‐like phenotype in aged mice

Aging is a negative regulator of general homeostasis, tissue function, and regeneration. Changes in organismal energy levels and physiology, through systemic manipulations such as calorie restriction and young blood infusion, can regenerate tissue activity and increase lifespan in aged mice. However, whether these two systemic manipulations could be linked has never been investigated. Here, we report that systemic GDF11 triggers a calorie restriction‐like phenotype without affecting appetite or GDF15 levels in the blood, restores the insulin/IGF‐1 signaling pathway, and stimulates adiponectin secretion from white adipose tissue by direct action on adipocytes, while repairing neurogenesis in the aged brain. These findings suggest that GDF11 has a pleiotropic effect on an organismal level and that it could be a linking mechanism of rejuvenation between heterochronic parabiosis and calorie restriction. As such, GDF11 could be considered as an important therapeutic candidate for age‐related neurodegenerative and metabolic disorders.     

Effect of yeast cell disruption on ADH activity for redox reactions with in situ cofactor regeneration in a continuous solid/gas bioreactor

It has recently been demonstrated that dried cells of Saccharomyces cerevisiae were able to produce alcohols and aldehydes in a solid/gas reactor with in situ cofactor regeneration. Since diffusion of gaseous substrates may be limited by the membrane and cell wall, cell disruption by sonication was used to improve oxidoreduction with ethanol and butyraldehyde as substrates. Results showed that partial cell disruption enhances the maximum conversion yield with the best results obtained after 2 min of sonication. Beyond this time, the ADH activity decreased. Better stability was observed in the pellet obtained after centrifugation indicating the importance of cell environment for enzyme stability. Tests on purified mitochondria showed that the ADH activity in cells was mainly cytoplasmic. The addition of oxidized cofactor did not change either the activity or the stability of the catalyst in a gaseous medium. The effect of water activity was studied on material obtained after 2 min of disruption and a reduction of critical water activity needed for revealing enzymatic activity was observed. With increasing a_w, the enzyme was active at a_w=0.3 while a water activity of 0.4 was required before disruption. Nevertheless, the best compromise between activity and stability was obtained in both cases for a water activity of 0.57.     

p58IPK-Mediated Attenuation of the Proapoptotic PERK-CHOP Pathway Allows Malignant Progression upon Low Glucose

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Highlights? Transformation-associated glucose shortage triggers ER stress ? The ER stress acts as barrier to malignancy by triggering UPR-dependent apoptosis ? p58^IPK expression removes the UPR barrier by attenuating its PERK-CHOP branch ? This adaptive mechanism enables implementation of UPR cytoprotective features