Enzymes ATPase

The phosphorylation reaction is also localized in the cell mitochondria. The enzyme ATP synthetase present in the mitochondrial membranes is involved in this reaction. The back reaction, which is the hydrolysis of ATP to ADP, occurs at other points of the ecu and involves another enzyme, ATPase. The concentrations of the main reaction components, ADP and ATP, in cytoplasm are about 1 mM. 

Another application of intermediate 50 lies in the synthesis of citrovireal 103 which is a metabolite of citreoviridine (104). This is an interesting polyene-pyrone toxin which has been isolated from penicillium citreoviride cultures. Citreoviridine has been shown to cause the Beri Beri disease which is acquired from eating infected rice. In effect the toxin 104 acts as an inhibitor of the enzyme ATPase. So far, several syntheses have been reported for optically active 103 which has thus served as a goal for developing new synthetic methodology (14). 

In the normal thyroid, NIS transports two Na and one V down the Na ion gradient generated by the activity of Na /K adenosine triphosphatase enzyme (ATPase) (Figure 102.2). If ATPase is blocked with ouabain, thyroid iodine uptake is also blocked. 

The inner particles, which at one point were believed to contain cytochromes, are now known to be devoid of respiratory enzymes and to contain a single enzyme—ATPase— which can be separated from and rebound to the membrane. 

Single-molecule spectroscopy has been used to address important problems in biology. One notable example is the visualization of some of the steps involved in the synthesis of ATP by the enzyme ATPase, which we discussed in Chapter 5. 

Frequently, the presence of ATPase in snake venoms is described. However, it is clear that the hydrolysis of ATP is due to the action of an exonuclease rather than the separate enzyme, ATPase. 

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