Transplasma membrane electron transport in plants

Different characteristics between menadione and menadione sodium bisulfite as redox mediator in yeast cell suspension

Menadione promoted the production of active oxygen species (AOS) in both yeast cell suspension and the crude enzymes from the cells, but menadione sodium bisulfite (MSB) had little effect on the production of AOS in the cell suspension. MSB kept the stable increase in the electron transfer from intact yeast cells to anode compared to menadione, but the electron transfer promoted by MSB was inhibited in permeabilized yeast cell suspension. Menadione promoted oxidation of NAD(P)H much faster than MSB in permeabilized yeast cell suspension, suggesting the oxidative stress due to consumption of NAD(P)H. The proliferation of yeast cells was inhibited by menadione under aerobic conditions rather than anaerobic conditions, and the inhibitory effect was reduced by superoxide dismutase and catalase. The effect of MSB on the proliferation was much smaller than that of menadione. The above facts suggest that harmless MSB promotes the electron transfer from plasma membrane of yeast cells to anode. On the other hand, harmful menadione might promote the electron transfer from cytosol and plasma membrane to anode and dissolved oxygen.

Study the effect of Vitamin K on intracellular NAD level in yeast by fluorescence spectrum

The intracellular NAD level plays a pivotal role in numerous biological processes such as rhythm, senescence, cancer and death. The study of the intracellular NAD level has been one of the "hotspots" in biomedical research. We investigated the effect of Vitamin K on intracellular NAD level in yeast by fluorescence spectrum in this paper. Plasma membrane redox system of yeast was found to be greatly promoted by the addition of Vitamin K(3) or Vitamin K(1). Ferricyanide reduction catalyzed by Vitamin K was accompanied by the decrease in intracellular NADH concentration and the increase in intracellular NAD level of yeast cells.

Triton X-100 inhibition of yeast plasma membrane associated NADH-dependent redox activities

Plasma membrane (PM) vesicles isolated from the yeast Saccharomyces cerevisiae (wild-type NCIM 3078, and a MG 21290 mutant pma 1-1) were used to monitor the effect of the detergents, 3-[(3-cholamidopropyl) dimethylammonio]-1-propane sulfonate (Chaps) and Triton X-100, on (H+)-ATPase (E.C. 3.6.1.35), NADH oxidase and NADH-hexacynoferrate (III)[HCF (III)] oxidoreductase (E.C. 1.6.99.3) activities. The results obtained show that Triton X-100 inhibited both membrane bound and solubilized NADH-dependent redox activities. The nature of this inhibition as determined for NADH-HCF(III) oxidoreductase was non-competitive and the Ki values for wild and mutant enzymes were 1.2 x 10(-5) M and 8.0 x 10(-6) M, respectively. The findings are interpreted, in view of the established reports, that the active site architecture of PM bound NADH-dependent oxidoreductase in yeast is likely to be different than in other eukaryotes.

Concanavalin A induced activity change in yeast PM-bound NADH-HCF(III) oxidoreductase

The activity of plasma membrane bound redox enzyme, NADH-HCF(III) oxidoreductase, in wild and mutant strains of the yeast Saccharomyces cerevisiae is modulated by Con A in a dose-dependent manner. The solubilized activity is enhanced at lower concentration and inhibited at higher concentration of Con A. The enzyme in mutant strain is more sensitive to inhibition. The activation of enzyme by Con A is suppressed in the presence of either alpha-methyl-D-mannoside or 2-deoxy-D-glucose, indicating the glycoproteic nature of enzyme as well as the resulting conformational change due to interaction with Con A as the factor for modulated activities. This was supported by recording the decrease in K(m) value of enzyme with respect to substrate NADH in the presence of lower concentration of Con A. The purified enzyme was more sensitive to lectin stimulation and, on the basis of comparative stimulatory effects of Con A and PSA on activity, it is likely that mannosyl moiety in enzyme is involved in binding the lectins to cause enzymic activation.

Transplasma membrane electron transport: enzymes involved and biological function

The notion of transmembrane electron transport is usually associated with mitochondria and chloroplasts. However, since the early 1970s, it has been known that this phenomenon also occurs at the level of the plasma membrane. Ever since, evidence has accumulated for the existence of a plethora of transplasma membrane electron transport enzymes. In this review, we discuss the various enzymes known, their molecular characteristics and their biological functions.

Plasma membrane electron transport coupled to Na(+) extrusion in the halotolerant alga Dunaliella

The halotolerant alga Dunaliella adapts to exceptionally high salinity and maintains low [Na(+)](in) at hypersaline solutions, suggesting that it possesses efficient mechanisms for regulating intracellular Na(+). In this work we examined the possibility that Na(+) export in Dunaliella is linked to a plasma membrane electron transport (redox) system. Na(+) extrusion was induced in Dunaliella cells by elevation of intracellular Na(+) with Na(+)-specific ionophores. Elevation of intracellular Na(+) was found to enhance the reduction of an extracellular electron acceptor ferricyanide (FeCN). The quinone analogs NQNO and dicumarol inhibited FeCN reduction and led to accumulation of Na(+) by inhibition of Na(+) extrusion. These inhibitors also diminished the plasma membrane potential in Dunaliella. Anaerobic conditions elevated, whereas FeCN partially decreased intracellular Na(+) content. Cellular NAD(P)H level decreased upon enhancement of plasma membrane electron transport. These results are consistent with the operation of an electrogenic NAD(P)H-driven redox system coupled to Na(+) extrusion in Dunaliella plasma membrane. We propose that redox-driven Na(+) extrusion and recycling in Dunaliella evolved as means of adaptation to hypersaline environments.

Cell membrane redox systems and transformation

Cell membrane redox systems carry electrons from intracellular donors and transport them to extracellular acceptors. This phenomenon appears to be universal. Numerous reviews have emphasized not only the bioenergetic mechanisms of redox systems but also the antioxidant defense mechanisms in which they participate. Moreover, significant progress has been made in the modulation of the membrane redox systems on cell proliferation. Because membrane redox systems play a key role in the regulation of cell growth, they need to be somehow linked into the signaling pathways resulting in either controlled or unregulated growth by both internal and external signals. Ultimately, these sequential events lead to either normal cell proliferation or cancer cell formation. However, much less is known about the involvement of membrane redox in transformation or tumorgenesis. In this review, the facts and ideas are summarized concerning the redox systems and tumorgenesis in several aspects, such as the regulation of cell growth and the effect on cell differentiation and on signaling pathways. In addition, information on a unique tumor-associated nicotinamide adenine dinucleotide (NADH) oxidase (tNOX) protein is reviewed.