scholarly journals Regulation of proton-translocating V-ATPases.

1997 ◽  
Vol 200 (2) ◽  
pp. 225-235 ◽  
Author(s):  
H Merzendorfer ◽  
R Gräf ◽  
M Huss ◽  
W R Harvey ◽  
H Wieczorek
Keyword(s):  
Gene Expression ◽  
Enzyme Activity ◽  
Plasma Membranes ◽  
Regulation Of Gene Expression ◽  
Transcriptional Level ◽  
Structural Domains ◽  
Sh Groups ◽  
Signalling Molecules ◽  
Membrane Spanning ◽  
Regulation Of Enzyme Activity

Vacuolar-type ATPases (V-ATPases) are proton-translocating enzymes that occur in the endomembranes of all eukaryotes and in the plasma membranes of many eukaryotes. They are multisubunit, heteromeric proteins composed of two structural domains, a peripheral, catalytic V1 domain and a membrane-spanning V0 domain. Both the multitude of locations and the heteromultimeric structure make it likely that the expression and the activity of V-ATPases are regulated in various ways. Regulation of gene expression encompasses control of transcription as well as control at the post-transcriptional level. Regulation of enzyme activity encompasses many diverse mechanisms such as disassembly/reassembly of V1 and V0 domains, oxidation of SH groups, control by activator and inhibitor proteins or by small signalling molecules, and sorting of the holoenzyme or its subunits to target membranes.

scholarly journals Temperature and the regulation of enzyme activity in poikilotherms. Fructose diphosphatase from migrating salmon

1969 ◽  
Vol 115 (4) ◽  
pp. 687-696 ◽  
Author(s):  
Hans W. Behrisch
Keyword(s):  
Enzyme Activity ◽  
Liver Cell ◽  
Functional Significance ◽  
Energy Charge ◽  
Low Energy ◽  
Biosynthetic Activity ◽  
Allosteric Inhibitor ◽  
High Fructose ◽  
Saturation Kinetics ◽  
Regulation Of Enzyme Activity

1. The calculated energy charge of the liver cell from migrating salmon is very low (0·464), in keeping with the extended starvation and high rates of muscular and biosynthetic activity of these organisms. 2. Affinity of fructose 1,6-diphosphatase for substrate increases with a decrease in temperature. 3. Arrhenius plots of the saturation kinetics are complex and suggest an interconversion of one or more forms of the enzyme; this interconversion is dependent on the identity of the cofactor. 4. Affinity of salmon fructose 1,6-diphosphatase for its allosteric inhibitor (AMP) is lower than in other fructose 1,6-diphosphatases and this enzyme–AMP interaction is largely insensitive to temperature. The functional significance of diminished AMP-sensitivity is that it allows normal or high fructose 1,6-diphosphatase activity during a low energy charge. 5. These findings suggest mechanisms for the maintenance of high rates of gluconeogenesis in salmon during spawning migration.

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