Phosphoryl groups, location

As discussed above, one of the two phosphoryl groups present in lipid A is linked to the glycosidic hydroxyl group of the reducing glucosamine residue in the disaccharide. The location of the second phosphoryl residue was identified in the following way... 

The acceptors in protein phosphorylation reactions are located inside cells, where the phosphoryl-group donor ATP is abundant. Proteins that are entirely extracellular are not regulated by reversible phosphorylation. Table 10.2 lists a few of the knovm protein kinases. Protein phosphatases reverse the effects of kinases by catalyzing the hydrolytic removal of phosphoryl groups attached to proteins. 

RNase A can use one-dimensional diffusion along a poly(dA) tract to accelerate the location of a uridine substrate. Use of this mechanism depends on the concentration of NaCl, as expected if the enzyme were binding to the nucleic acid by nonspecific interactions with phosphoryl groups. Binding of the enzymic active site to adenosine residues is 20-fold weaker than to uridine residues, which could enhance the ability of the enzyme to slide along the poly(dA) tract. 

The suffix -mutase indicates another type of isomerase. Notice that the chemical formulas of the substrate and reactant are the same. The only difference is in the location of the phosphoryl group. 

The primary mechanism of action of OP pesticides is inhibition of AChE. AChE is an enzyme found in the central nervous system (CNS) and the peripheral nervous system, and its normal physiologic action is to metabolize acetylcholine (ACh), a neurotransmitter. OPs inactivate AChE by phosphorylating the. serine hydroxyl group located at the active site of AChE. The phosphorylation occurs by loss of an OP leaving group and establishment of a covalent bond with AChE. 

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