Ebook Harper’s illustrated biochemistry (26th edition): Part 12
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Ebook Harper’s illustrated biochemistry (26th edition): Part 12
SECTION IVStructure, Function, & Replication of Informational MacromoleculesNucleotidesVictor w. Rodwell, PhD33BIOMEDICAL IMPORTANCENucleotides—the mo Ebook Harper’s illustrated biochemistry (26th edition): Part 12onomer units or building blocks of nucleic acids—serve multiple additional functions. I hey form a part of many coenzymes and serve as donors of phosphoryl groups (eg, ATP or GTP), of sugars (eg, UDP- or GDP-sugars), or of lipid (eg, CDP-acylglyc-crol). Regulator}' nucleotides include the second mes Ebook Harper’s illustrated biochemistry (26th edition): Part 12sengers cAMP and cGMP, rhe control by ADP of oxidative phosphorylation, and allosteric regulation of enzyme activity by ATP, AMP, and CTP. Synthetic pEbook Harper’s illustrated biochemistry (26th edition): Part 12
urine and pyrimidine analogs that contain halogens, thiols, or additional nitrogen arc employed for chemotherapy of cancer and AIDS and as suppressorsSECTION IVStructure, Function, & Replication of Informational MacromoleculesNucleotidesVictor w. Rodwell, PhD33BIOMEDICAL IMPORTANCENucleotides—the mo Ebook Harper’s illustrated biochemistry (26th edition): Part 12eterocycles, cyclic compounds whose rings contain both carbon and other elements (hetero atoms). Note that the smaller pyrimidine has the longer name and the larger purine the shorter name and that their six-atom rings are numbered in opposite directions (Figure 33-1). The planar character of purine Ebook Harper’s illustrated biochemistry (26th edition): Part 12s and pyrimidines facilitates their close association, or "stacking," which stabilizes double-stranded DNA (Chapter 36). The 0X0 and amino groups of pEbook Harper’s illustrated biochemistry (26th edition): Part 12
urines and pyrimidines exhibit keto-enol and aminc-imine tautomerism (Figure 33-2), but physiologic conditions strongly favor the amino and 0X0 forms.SECTION IVStructure, Function, & Replication of Informational MacromoleculesNucleotidesVictor w. Rodwell, PhD33BIOMEDICAL IMPORTANCENucleotides—the mo Ebook Harper’s illustrated biochemistry (26th edition): Part 12ucleotidesNucleosides arc derivatives of purines and pyrimidines that have a sugar linked to a ring nitrogen. Numerals with a prime (eg, 2' or i') distinguish atoms of the sugar from those of rhe heterocyclic base. The sugar in ribonucleosides is D-ribosc, and in dcoxyribonuclco-sides it is 2-deoxy- Ebook Harper’s illustrated biochemistry (26th edition): Part 12D-ribose. The sugar is linked co the heterocyclic base via a |ỉ-N’-glycosidic bond, almost always ro N-l of a pyrimidine or to N-9 of a purine (FigureEbook Harper’s illustrated biochemistry (26th edition): Part 12
33-3).Figure 33-2. Tautomerism of the 0X0 and amino functional groups of purines and pyrimidines.286OH OHAdenosineCytidineUridineFigure 33-3. RibonucSECTION IVStructure, Function, & Replication of Informational MacromoleculesNucleotidesVictor w. Rodwell, PhD33BIOMEDICAL IMPORTANCENucleotides—the mo Ebook Harper’s illustrated biochemistry (26th edition): Part 12 5'-nucleotidcs arc nucleosides with a phosphoryl group on the 3*- or 5'-hydroxyl group of the sugar, respectively. Since most nucleotides are 5'-, the prefix “5 -” is usually omitted when naming them. ƯMP and dAMP thus represent nucleotides with a phosphoryl group on C-5 of the pentose. Additional Ebook Harper’s illustrated biochemistry (26th edition): Part 12phosphoryl groups linked by acid anhydride bonds to the phosphoryl group of a mononucleotide form nucleoside diphosphates and triphosphates {Figure 33Ebook Harper’s illustrated biochemistry (26th edition): Part 12
-4).Steric hindrance by the base restricts rotation about the |3-N-glycosidic bond of nucleosides and nuAdenosine 5'-dipho$phate (ADP)Adenosine 5'-triSECTION IVStructure, Function, & Replication of Informational MacromoleculesNucleotidesVictor w. Rodwell, PhD33BIOMEDICAL IMPORTANCENucleotides—the mo Ebook Harper’s illustrated biochemistry (26th edition): Part 12 both conformers occur in nature, anti conformers predominate. Table 33-1 lists the major purines and pyrimidines and their nucleoside and nucleotide derivatives. Single-letter abbreviations are used to identify adenine (A), guanine (G), cytosine (C), thymine (D, and uracil (Ư), whether free or pres Ebook Harper’s illustrated biochemistry (26th edition): Part 12ent in nucleosides or nucleotides. The prefix “d” (deoxy) indicates that the sugar is 2'-deoxy-D-ribose (eg, dGTP) (Figure 33-6).Nucleic Acids Also CoEbook Harper’s illustrated biochemistry (26th edition): Part 12
ntainAdditional BasesSmall quantities of additional purines and pyrimidines occur in DNA and RNAs. Examples include 5-mcthyl-cytosine of bacterial andSECTION IVStructure, Function, & Replication of Informational MacromoleculesNucleotidesVictor w. Rodwell, PhD33BIOMEDICAL IMPORTANCENucleotides—the mo Ebook Harper’s illustrated biochemistry (26th edition): Part 12d anti conformers of adenosine differ with respect to orientation about the N-gly-cosidic bond.288 I CHAPTER 33Table 33-1. Bases, nucleosides, and nucleotides.AMPFigure 33-6. AMP, dAMP, UMP, and TMP. Ebook Harper’s illustrated biochemistry (26th edition): Part 12SECTION IVStructure, Function, & Replication of Informational MacromoleculesNucleotidesVictor w. Rodwell, PhD33BIOMEDICAL IMPORTANCENucleotides—the moGọi ngay
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