Plasma membrane-bound reductase

W. Briiggemann, P. R. Moog, H. Nakagawa, P. Janiesch, and P. J. C. Kuiper, Plasma membrane-bound NADH-Fe -EDXA reductase and iron deficiency in tomato. (Lycopcrsicon escidentiim). Is there a turbo reductase Physiol. Plant 79 339 (1991). 

The results of this work support the view that Fe-WEHS complex may serve as a natural substrate for the inducible plasma-membrane-bound Felll-chelate reductase in Strategy I plants (Pinton et al., 1999b). In Strategy II plants, an indirect mechanism, conceivably operating via ligand exchange between the humic fraction and the phytosiderophores released, appears to be involved in the use of Fe bound to WEHS. 

Stohr, C., Schuler, F., and Tischner, R., 1995, Glycosyl-phosphatidylinositol-anchored proteins exist in the plasma membranes of Chlorella Saccharophila (Kruger) Nadson Plasma-membrane-bound nitrate reductase as an example. Planta 196 284-287. 

Tischner, R. A., Ward, M. R., and Huffaker, R. C. (1989). Evidence for a plasma-membrane-bound nitrate reductase involved in nitrate uptake of Chlorella sorokiniana. Planta. 178, 19—24. 

Figure 7 Mixld for iron (Fe) deficiency induced changes in root physiology and rhizo-sphere chemistry associated with Fc acquisition in strategy I plants. (Modified froin Ref. 1.) A. Stimulation of proton extru.sion by enhanced activity of the plasnialemma ATPase —> Felll solubilization in the rhizospherc. B. Enhanced exudation of reductanls and chela-tors (carhoxylates. phenolics) mediated by diffusion or anion channels Pe solubilization by Fein complexation and Felll reduction. C. Enhanced activity of plasma membrane (PM)-bound Felll reductase further stimulated by rhizosphere acidificalion (A). Reduction of FolII chelates, liberation of Fell. D. Uptake of Fell by a PM-bound Fell transporter.

A second example of a membrane-bound arsenate reductase was isolated from Sulfurospirillum barnesii and was determined to be a aiPiyi-heterotrimic enzyme complex (Newman et al. 1998). The enzyme has a composite molecular mass of 100kDa, and a-, P-, and y-subunits have masses of 65, 31, and 22, respectively. This enzyme couples the reduction of As(V) to As(III) by oxidation of methyl viologen, with an apparent Kra of 0.2 mM. Preliminary compositional analysis suggests that iron-sulfur and molybdenum prosthetic groups are present. Associated with the membrane of S. barnesii is a h-type cytochrome, and the arsenate reductase is proposed to be linked to the electron-transport system of the plasma membrane. 

The recently isolated Desulfotomaculum strain Ben-RB is able to grow using lactate as a substrate and arsenate as the sole electron acceptor (Macy et al. 2000). It has been proposed that arsenate reductase is associated with the respiratory chain of this organism, because >98% of the arsenate reductase bound to the plasma membrane. 

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