Phosphorylation phosphate

DNA and RNA are formed of nucleotides. Each nucleotide or nucleoside is composed of a purine or pyrimidine base linked to the 1-position of a ribose sugar in the case of RNA and a 2 -deoxyribose sugar in the case of DNA.155 The 5 position is phosphorylated in the case of a nucleotide, while the nucleoside is not phosphorylated therefore, nucleotides are nucleoside phosphates. Phosphorylation can include one, two, or three phosphate groups. The most familiar example of a phosphorylated nucleotide is phosphorylated adenosine, which occurs as the mono-, di-, and triphosphate (AMP, ADP, and ATP, respectively) and is a principal means of energy storage in biological systems. 

Energy charge. The fractional degree to which the AMP-ADP-ATP system is filled with high-energy phosphates (phosphoryl groups). 

Kinase. An enzyme catalyzing phosphorylation of an acceptor molecule, usually with ATP serving as the phosphate (phosphoryl) donor. 

Fig. 115 The dependence of the rate of fructose 6-phosphate phosphorylation by phosphofructokinase on the presence of low and high concentrations of ATP.

Rearrangements in the naphthalene series are exemplified by that of dialkyl 1 -naphthalenyl phosphates into dialkyl (2-hydroxynaphthalenyl)phosphonates and, more surprisingly, that of dialkyl 2-naphthalenyl phosphates into dialkyl (3-hydroxy-2-naph-thalenyl)phosphonates. The most recent extension of the rearrangement is in the pyridine series. In a series of diethyl pyridinyl phosphates, phosphoryl migration occurred from oxygen on C(3) to C ), or if the latter position was blocked, to C(2), and from oxygen... 

D-tagatose 6-phosphate kinase kinase, tagatose 6-phosphate (phosphorylating) tagatose 6-phosphate kinase (phosphorylating) tagatose-6-phosphate kinase... 

S diphosphate + microsomal polypeptides <1> (Reversibility <1> [1]) [1] P phosphate + phosphorylated microsomal polypeptides... 

Fig. 11-11 Regulation of glycogen synthase by phosphorylation, dephosphorylation, and glucose 6-phosphate. Phosphorylation of glycogen synthase takes place via at least seven different protein kinases as indicated. cAMP denotes cyclic AMP. The dashed arrows with adjacent -t and - signs denote activation or inhibition, respectively.

Protein kinases Modulators. The importance of phosphorylation is underlined by the fact that one in three cytoplasmic proteins contains covalently bound phosphate. Phosphorylation modifies proteins by addition of negatively charged groups to serine, threonine and tyrosine, thus altering the chemical properties of proteins substantially. As a result, a protein may then recognize, bind, activate, deactivate, phosphorylate or dephosphorylate its substrate. Phosphorylation can switch enzymes on and off (subsection 11.5.2). 

Phosphoryl choline. See Choline phosphate Phosphoryl trichloride. See Phosphorus oxychloride... 

DeoxyribOM phosphates phosphorylated derivatives of the deoxypentose, l-deoxy-n-rihose. They are biosynthesized by reduction of ribose phosphates in the course of nucleotide synthesis There are two enzymes in E. coli which reduce cytidine diphosphate to deoxycytidine diphosphate. Deoxytibose 5- and 1-phosphate form an equilibrium mixture in the presence of phosphopentomutase (EC 2.7.5.6). 

Ribose phosphates phosphorylated derivatives of ribose. Ribose is phosphorylated in position 5 by the action of ribokinase (EC 2.7.1.15) and ATP ribose 5-phosphate is also produced in the Pentose phosphate cycle (see), and in the Calvin c cle (see) of photosynthesis. Phosphoribomutase cat yses the interconversion of ribose 5-phospbate and ribose 1-phosphate, and the cosubstrate of this reaction is ribose l,5-f>isphosphate. 5-Phosphoribosyl 1-pyrophos-phate donates a ribose 5-phosphate moiety in the de novo biosynthesis of purine and pyrimidine nucleotides (see Purine biosynthesis. Pyrimidine biosynthesis), in the Salvage pathway (see) of purine and pyrimidine utilization, in the biosynthesis of L-Histi-dine (see) and L-Tryptophan (see) and in the conversion of nicotinic acid into nicotinic acid ribotide (see Pyridine nucleotide cycle). Ribose 1-phosphate can also take part in nucleotide synthesis (see Salvage pathway). 

The most important type of acid anhydride in biochemistry is that between two molecules of phosphoric acid, as exemplified by the two terminal bonds of ATP (p. 67), but the pyrophosphate bond is not the only type of energy-rich bond as can be seen from Table XI. Mixed anhydrides of carboxylic and phosphoric acids (acyl-phosphates), phosphorylated enol groups (enolphosphates), phosphorylated guanidine groups (guanidine phosphates), compounds of sulphhydryl groups with phosphoric or carboxylic acids (thioesters or thiophosphates), all these types of compound are energy-rich. 

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