Chapter27

Chapter27 - BCH 4054 Fall 2000 Chapter 27 Lecture Notes...

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Chapter 27, page 1 BCH 4054 Fall 2000 Chapter 27 Lecture Notes Slide 1 Chapter 27 Nucleotide Metabolism Slide 2 Review Nucleotide Structure and Nomenclature (Chapter 11) • Composition • Heterocyclic Base • Pentose • Phosphate • Besides being the building blocks of nucleic acids, nucleotides have many roles in metabolism Slide 3 Heterocyclic Bases—Pyrimidines DNA and RNA RNA only DNA only
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Chapter 27, page 2 Slide 4 Heterocyclic Bases –Purines The Purine Ring System: N N N H N NH 2 Adenine Guanine NH N N H N O NH 2 Slide 5 Nucleosides β glycosidic linkage at N-1 of pyrimidine and N-9 of purine N N N N NH2 O OH OH H H H H HO Adenosine N NH 2 O N O OH OH H H H H HO Cytidine Slide 6 Nucleotides • Nucleotides are phosphate esters of nucleosides • Named as “nucleoside-X’-phosphate” where X’ is the ribose position to which the phosphate is attached • Example: adenosine-5’- monophosphate N N N N NH2 O OH OH H H H H O P -O O- O
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Chapter 27, page 3 Slide 7 “C-1” Metabolism • Before beginning discussion of purine and pyrimidine biosynthesis, we need to discuss metabolism of one-carbon units. • Biotin was introduced as a “carrier” of CO 2 • Other C-1 units include methanol , formaldehyde , and formic acid • These are metabolized while covalently bound to tetrahydrofolic acid • Review chapter 18, pages 602-603 Slide 8 C CH 2 O H 2 N N H N N N O H N CHCH 2 CH 2 COO - COO - HN 5 6 7 8 9 10 Folic Acid (Pteroyl Glutamic Acid) Pterin p-amino benzoic acid glutamic acid FolicAcid Folic acid derivatives with up to 7 glutamate residues are found. The glutamates are attached through amide linkage to the gamma carboxyl group. Sulfa drugs, among the earliest antibiotics, are structural analogues of p-aminobenzoic acid and inhibit the biosynthesis of folic acid. Slide 9 Reduced Forms of Folic Acid • Reductions occur with NADPH • See Fig 18.35 CH 2 O H 2 N N H N N CH 2 H N HN 5 10 DHF Dihydrofolate same CH 2 O H 2 N N H N N H CH 2 H N HN H 5 10 THF Tetrahydrofolate same
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Chapter 27, page 4 Slide 10 “C-1” Derivatives of THF (See also Table 18.6, p 603) • Methanol oxidation level (Ox. No. –2) • N 5 -methyl THF • Formaldehyde oxidation level (Ox. No. 0) • N 5 ,N 10 -methylene THF • Formic acid oxidation level (Ox. No. +2) • N 5 -formyl THF and N 10 -formyl THF • N 5 -formimino THF • N 5 , N 10 -methenyl THF The oxidation number of carbon in CO 2 is +4. Slide 11 • Donor of methyl group in methionine biosynthesis: homocysteine + N 5 -methyl THF methionine + THF CH 2 O H 2 N N H N N CH 2 H N NH H 5 10 CH 3 N 5 Methyl THF N 5 Methyl THF Slide 12 CH 2 O H 2 N N H N N CH 2 H N NH H 5 10 H 2 C N 5 ,N 10 Methylene THF THF serine glycine N 5 Methyl THF NAD NADH N 5 , N 10 Methylene THF The pyridoxal phosphate derivative of serine is involved in this reaction. Recall we discussed how that
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This note was uploaded on 11/27/2011 for the course BSC 5936 taught by Professor Staff during the Spring '08 term at FSU.

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Chapter27 - BCH 4054 Fall 2000 Chapter 27 Lecture Notes...

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