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9: Phosphate Transfer Reactions

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  • This chapter is about the chemistry of phosphates, a ubiquitous functional group in biomolecules that is based on phosphoric acid.

    • 9.1: Prelude to Phosphate Transfer Reactions
      This chapter is about the chemistry of phosphates, a ubiquitous functional group in biomolecules that is based on phosphoric acid.
    • 9.2: Overview of Phosphate Groups
      Phosphate is everywhere in biochemistry. As we were reminded in the introduction to this chapter, our DNA is linked by phosphate. The function of many proteins is regulated - switched on and off - by enzymes which attach or remove a phosphate group from the side chains of serine, threonine, or tyrosine residues.
    • 9.3: Phosphate Transfer Reactions - An Overview
      In a phosphate transfer reaction, a phosphate group is transferred from a phosphate group donor molecule to a phosphate group acceptor molecule. A very important aspect of biological phosphate transfer reactions is that the electrophilicity of the phosphorus atom is usually enhanced by the Lewis acid (electron-accepting) effect of one or more magnesium ions.
    • 9.4: ATP, The Principal Phosphate Group Donor
      Thus far we have been very general in our discussion of phosphate transfer reactions, referring only to generic 'donor' and 'acceptor' species. It's time to get more specific. The most important donor of phosphate groups in the cell is a molecule called adenosine triphosphate, commonly known by its abbreviation ATP.
    • 9.5: Phosphorylation of Alcohols
      A broad family of enzymes called kinases catalyze transfer of a phosphate group from TP to an alcohol acceptor. Mechanistically, the alcohol oxygen acts as a nucleophile, attacking the electrophilic g-phosphorus of TP and expelling ADP.
    • 9.6: Phosphorylation of Carboxylates
      Thus far we have seen hydroxyl oxygens and phosphate oxygens acting as nucleophilic accepting groups in ATP-dependent phosphate transfer reactions. Carboxylate oxygens can also accept phosphate groups from ATP. This typically happens in two different ways.
    • 9.7: Hydrolysis of Organic Phosphates
      While kinase enzymes catalyze the phosphorylation of organic compounds, enzymes called phosphatases catalyze dephosphorylation reactions.
    • 9.8: Phosphate Diesters in DNA and RNA
      Phosphate diesters play an absolutely critical role in nature - they are the molecular 'tape' that connect the individual nucleotides in DNA and RNA via a sugar-phosphate backbone.
    • 9.9: The Organic Chemistry of Genetic Engineering
      Many enzymes that catalyze reactions involving the phosphate diester bonds of DNA have been harnessed for use in genetic engineering - techniques in which we copy, snip, and splice DNA in order to create custom versions of genes. The tools of genetic engineering have become indispensable and commonplace in the past decade, and most researchers working on the biological side of chemistry use them extensively.
    • 9.E: Phosphate Transfer Reactions (Exercise)
    • 9.S: Phosphate Transfer Reactions (Summary)
    • 9.10: NMR of phosphorylated compounds
      Because so many biological molecules contain phosphoryl groups, it is worthwhile to look at how scientists use NMR to determine the structure of these molecules. Recall from section 5.1 that 31P , the most abundant isotope of phosphorus, is NMR active: it can be directly observed by 31P−NMR , and indirectly observed in 1H−NMR and 13C−NMR through its spin-coupling interactions with neighboring protons and carbons, respectively.