NTPase enzymes

Since the pioneering work of Kleymann et al. (2002), Betz et al. (2002), Baumeister et al. (2007), and Crute et al. (2002), who showed that compounds identified as inhibitors of the helicase-primase enzyme complex could alleviate herpesvirus-induced disease in animal models, the attention of researchers developing antiviral compounds has been drawn more and more towards the virus-encoded helicases, particularly those of Herpes viruses and of RNA viruses such as Hepatitis C Virus (HCV) and SAKS coronavirus (SARS-CoV). Enzyme activity is usually assayed by measuring NTPase activity in the presence of an appropriate nucleic acid co-substrate although, more recently, novel fiuorimetric and luminescence principles have been applied to the measurement of strand unwinding and/or translocation of the protein along the nucleic acid (Frick 2003, 2006). 

The molecular mechanisms underlying the detrimental effects caused by aluminum have yet to be fully understood [31]. The toxicological mechanisms of aluminum in plants or in animals probably involve alterations in many enzyme activities. There is a large number of proteins which requires nucleoside phosphates as substrates or is regulated by nucleoside phosphates, therefore aluminum can potentially interfere with the normal functions of these proteins [18]. Thus, it is important to understand some reactions that involve aluminum and nucleotides. In this review we are going to focus on the alterations caused by this metal in some enzymes that hydrolyze or transfer phosphate groups of nucleotides, like NTPases, NTPDases, and kinases. 

Figure 18.25 Structure of ATP synthase. A schematic structure is shown along with representations of the components for which structures have been determined to high resolution. The P-(oop NTPase domains of the a and (3 subunits are indicated by purple shading. Notice that part of the enzyme complex is embedded in the inner mitochondrial membrane, whereas the remainder resides in the matrix. [Drawn from 1E79,pdb and ICOV.

A coiiimun catalytic core in type II restriction enzymes (p. 266) P-loop NTPase domains (p. 270)... 

Overall, the altered responses of hepatic nuclei of rats fed a CD diet to tryptophan are difficult to explain. Nevertheless, several findings merit comments. The failure of the livers of rats fed the CD diet to show increases in [14C]orotate-labeled nuclear RNA release in response to tryptophan (either tube-fed acutely or added to the diet) is consistent with the lack of increase in nuclear NTPase activity in the feeding experiments. This enzyme has been demonstrated to show increased activity in hepatic nuclei of normal animals... 

Relate the P-loop of kinases to the phosphoryl group of enzyme-bound ATP, and appreciate the ubiquity of P-loop NTPase domains. 

Myosin is an NTPase hydrolase enzyme. Nucleoside triphosphatases (NTPases) are one of the most important enzymes in living cells. A very large number of NTPase enzymes associated with a wide range of biological functions are known. 

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