Active sites from adenosine triphosphate

Treatment of 9-(/ -D-ribofuranosyluronic acid)adenine with diphenylphosphoro-chloridate and orthophosphate or tripolyphosphate yields (62) and (63), which, although unstable, inhibit rabbit AMP aminohydrolase and pyruvate kinase, respectively, with behaviour characteristic of active-site-specific reagents.98 Adenylate kinases from several sources are inactivated by iV6-[2- and 4-fluorobenzoyl]-adenosine-5 -triphosphates, with kinetics characteristic of active-site labelling, although these compounds were without effect on yeast hexokinase and rabbit pyruvate kinase.99... 

As an example of enzyme action, look in Figure 24.11 at the enzyme hexose kinase, which catalyzes the reaction of adenosine triphosphate (ATP) with glucose to yield glucose-6-phosphate and adenosine diphosphate (ADP). The enzyme first binds a molecule of ATP cofactor at a position near the active site, and glucose then bonds to the active site with its C6 hydroxyl group held rigidly in position next to the ATP molecule. Reaction ensues, and the two products are released from the enzyme. 

Firefly luciferase catalyzes the reaction of adenosine triphosphate and a substituted benzothiazole luciferin. The quantum yield of the reaction is high and therefore measurement of the enzyme offers good sensitivity. Coupling of luciferase to other molecules is a problem because there is a highly reactive amino group in the active site that must be protected from reaction with coupling rei ents (36, 37). 

The biocidal activity of hypochlorous acid arises from the fact that it is able to diffuse through the cell wall and membrane to attack the cytoplasm within the cell to produce chemically stable nitrogen-chlorine bonds with cell proteins. In addition active sites on certain co-en2yme sulphydryl groups are affected, so that the intermediate chemical transformations that lead to the production of adenosine triphosphate (ATP), are blocked thereby affecting respiration. 

S ATP + deoxyadenosine <1-10> (<1> transfers a phospho group from specific nucleoside 5 -triphosphate donors to 5 -position of deoxyadenosine [1] <1> no activity with adenosine and guanosine [1] <2> no activity with cytidine, uridine, guanosine, deoxyguanosine and thymidine [3] <4> enzyme bears two separate but interacting active sites for deoxyadenosine and deoxycytidine kinase activity [5] <4> enzyme exists in two heterodimeric complexes, complex 1 deoxycytidine/deoxyadenosine kinase and complex II deoxyguanosine/deoxyadenosine kinase [6] <3> enzyme has both adenosine kinase and deoxyadenosine kinase activity [14]) (Reversibility <1-10> [1-9,11,12,15]) [1-9, 11, 12, 14, 15]... 

---