Programming in situ accelerated DNA walkers in diffusion-limited microenvironments

In situ accelerated DNA walkers in diffusion-limited microenvironments are reported and utilized to monitor cytoplasmic enzyme catalysis and pathways.

Serum Aminotransferases and the Severity of Asthma

The serum enzymes are ideal diagnostic or prediction markers. Aspartate aminotransferase (AST), a mitochondrial and cytoplasmic enzyme, is one of the well-known markers of hepatic, myocardial or skeletal muscle cytolysis, while alanine aminotransferase (ALT) is mainly a hepatic cytoplasmic enzyme. The normal plasmatic values of AST and of ALT reflect a physiological cell turnover. Therefore, both high and low levels of serum liver enzymes might have a clinical significance. We have conducted a retrospective study targeting the association between the serum AST and ALT levels and the lung function impairment among patients with occupational asthma but without hepatic, cardiac, renal or muscular disorders. Our data show a significant relation (R = 0.54, p [0.05) between the parameters of obstructive ventilator syndrome and AST and ALT levels, respectively (R =0.42, p [0.05). If this relation is confirmed in prospective studies, serum AST and ALT could become useful markers in monitoring asthma patients.

NADP+ Reduction with Reduced Ferredoxin and NADP+ Reduction with NADH Are Coupled via an Electron-Bifurcating Enzyme Complex in Clostridium kluyveri

ABSTRACT It was recently found that the cytoplasmic butyryl-coenzyme A (butyryl-CoA) dehydrogenase-EtfAB complex from Clostridium kluyveri couples the exergonic reduction of crotonyl-CoA to butyryl-CoA with NADH and the endergonic reduction of ferredoxin with NADH via flavin-based electron bifurcation. We report here on a second cytoplasmic enzyme complex in C. kluyveri capable of energetic coupling via this novel mechanism. It was found that the purified iron-sulfur flavoprotein complex NfnAB couples the exergonic reduction of NADP+ with reduced ferredoxin (Fdred) and the endergonic reduction of NADP+ with NADH in a reversible reaction: Fdred 2− + NADH + 2 NADP+ + H+ = Fdox + NAD+ + 2 NADPH. The role of this energy-converting enzyme complex in the ethanol-acetate fermentation of C. kluyveri is discussed.

Experimental and Theoretical Bases of Specific Affinity, a Cytoarchitecture-Based Formulation of Nutrient Collection Proposed To Supercede the Michaelis-Menten Paradigm of Microbial Kinetics

ABSTRACT A theory for solute uptake by whole cells was derived with a focus on the ability of oligobacteria to sequester nutrients. It provided a general relationship that was used to obtain the kinetic constants for in situ marine populations in the presence of naturally occurring substrates. In situ affinities of 0.9 to 400 liters g of cells−1 h−1 found were up to 103 times smaller than those from a “Marinobacter arcticus ” isolate, but springtime values were greatly increased by warming. Affinities of the isolate for usual polar substrates but not for hydrocarbons were diminished by ionophores. A kinetic curve or Monod plot was constructed from the best available data for cytoarchitectural components of the isolate by using the theory together with concepts and calculations from first principles. The order of effect of these components on specific affinity was membrane potential > cytoplasmic enzyme concentration > cytoplasmic enzyme affinity > permease concentration > area of the permease site > translation coefficient > porin concentration. Component balance was influential as well; a small increase in cytoplasmic enzyme concentration gave a large increase in the effect of permease concentration. The effect of permease concentration on specific affinity was large, while the effect on Km was small. These results are in contrast to the Michaelis-Menten theory as applied by Monod that has uptake kinetics dependent on the quality of the permease molecules, with Km as an independent measure of affinity. Calculations demonstrated that most oligobacteria in the environment must use multiple substrates simultaneously to attain sufficient energy and material for growth, a requirement consistent with communities largely comprising few species.

α-glutathione s-transferase (α-GST) release, an early indicator of carbon tetrachloride hepatotoxicity in the rat

1 The use of the cytoplasmic enzyme, alpha glutathione s-transferase (α-GST) as an early index of carbon tetrachloride (CCl4) toxicity in the rat was investigated and compared with a standard enzyme marker, aspartate aminotransferase (AST). The hepatotoxic effects of CCl 4 in the rat were determined in a time and dose-response study. 2 Following CCl 4 exposure, α-GST release was shown to be an earlier and more sensitive biomarker of hepatotoxicity than AST. 3 Significant increases in α-GST were detected 2 h after CCl4 exposure. Using the enzyme marker AST, this early hepatotoxic injury went undetected. At 6 and 16 h, α-GST was also a more sensitive indicator of hepatotoxicity than AST. 4 α-GST release was significantly increased at a dose of 5 μl/kg, the lowest concentration of CCl4 administered and clearly responded in a dose-dependent manner with increasing doses of CCl4. In contrast, release of AST did not reach statistical significance until a dose of 25 μl/kg. 5 Thus, these findings indicate that α-GST is a more sensitive and more accurate reflector of CCl4 induced hepatotoxicity than AST.