미생물의 대사 -2 Microbial Metabolism

 Phosphorylation : Generation of ATP Photophosrylation ( 광인산화 ) Oxidative phosphorylation ( 산화적 인산화 ) Substrate level phosphorylation ( 기질 수준 인산화 ) Kinase Phosphatase Assimilation of Phosphorus ( 인의 동화반응 )

Assimilation of Sulfur ( 황의 동화반응 )

Assimilation of Nitrogen ( 질소의 동화반응 )

 Amino acid biosynthetic pathway Pyruvic acid family : alanine, valine, leucine Glutamic acid family : glutamic acid, glutamine proline, arginine Aspartic acid family : aspartic acid, asparagine lysine, threonine, isoleucine, methionine Aromatic amino acid(shikimic acid) family : phyenylalanine, tyrosine, tryptophan Serine family : serine, glycine, cysteine Histidine Biosynthesis of Amino acids

 Intermediates TCA cycle and Glycolysis Used as carbon skeletons for amino acids, … Needed for Energy generation  Anaplerotic reactions ( 보충반응 ) Greek ἀ νά= 'up' and πληρόω= 'to fill‘ Replenish intermediates of TCA cycle and glycolysis that have been extracted for biosynthesis (cataplerotic reactions) 1. Oxaloacetate from pyruvate from phosphoenol pyruvate (PEP) from aspartate 2. α-ketoglutarate from glutamate 3. Succinyl CoA from β-oxidation of fatty acids 4. Fumarate from adenylosuccinate 5. Malate from pyruvate 6. Glyoxylate cycle Anaplerotic reactions

 A variation of the TCA cycle  Utilizes 5/8 enzymes associated with the TCA cycle citrate synthase, aconitase, succinate dehydrogenase, fumarase, malate dehydrogenase  Key enzymes isocitrate lyase (ICL) isocitrate → glyoxalate, succinate (TCA: α-ketoglutarate) bypasses the decarboxylation steps in the TCA cycle malate synthase (MS) glyoxalate + acetyl-CoA → malate  Centers on the conversion of acetyl-CoA to succinate for the synthesis of carbohydrates Allow simple carbon compounds to be used in the synthesis of macromolecules (shunt, pathway) Glyoxylate cycle (shunt, pathway)

Glyoxylate cycle

 Purines & Pyrimidines  Building blocks of DNA and RNA  Energy carrier : ATP, GTP  Components of co-enzymes : NAD and FAD  Signal transduction : cAMP & cGMP as ‘second messengers ’  De-novo biosynthesis & Salvage pathway  De-novo biosynthesis Synthesized as ribonucleotides from simple precursors Deoxyribonucleotides from ribonucleotides  Salvage pathway Recover bases and nucleosides formed during the degradation of RNA and DNA Biosynthesis of nucleotides

 Purines are synthesized as ribo-nucleotides (nitrogen base + ribose sugar + phosphate) rather than as free bases  Adenine and guanine are derived from IMP IMP : inosine-5’-monophosphate  Starts with the production of PRPP by PRPP synthetase activated by inorganic phosphate inactivated by purine ribonucleotides. PRPP : 5-phospho-α-D-ribosyl 1-pyrophosphate  The first committed step for purine synthesis PRPP + L-Glutamine + H 2 O → PRA + L-Glutamate + PPi PRA : 5'-phosphoribosylamine PPi : pyrophosphate amidophosphoribosyltransferase (glutamine-PRPP amidotransferase) activated by PRPP and inhibited by AMP, GMP and IMP Biosynthesis of Purines

Biosynthesis of Pyrimidines

 Antibacterial sulfonamides : sulfa drugs Competitive inhibitors of PABA PABA (para-aminobenzoic acid) Precursor of folic acid synthesis (in bacteria) Folic acid : required for nucleotide synthesis Inhibit nucleotide synthesis

Biosynthesis of Lipids

 Peptidoglycan biosynthesis 1. Synthesis of peptidoglycan monomers in the cytosol 2. Transport of the monomers across the cell membrane bactoprenol : a lipid membrane carrier 3. Insertion of the monomers into the existing peptidoglycan 4. Formation of cross-linkage Peptidoglycan biosynthesis

Stage 1. Synthesis of peptidoglycan monomers in cytosol From glutamine and fructose-6-phosphate UDP-N-acetylglucosamine (UDP-GlcNAc, UDP-NAG) UDP-N-acetylmuramic acid (UDP-MurNAc, UDP-NAM) UDP-MurNAc pentapeptide UDP : uridine triphosphate, energy source Stage 2. Transport of peptidoglycan monomers across the cell membrane Bactoprenol : a lipid carrier that carries peptidoglycan precursors through the cell membrane 1. Generation of Lipid-PP-MurNAc pentapeptide-GlcNAc 2. Transportation of the disaccharide through the membrane Peptidoglycan biosynthesis

Stage 3. Synthesis of peptidoglycan 1. Addition of the disaccharide to the growing glycan chain (transglycosylation) 2. Formation of cross-linkage (transpeptidation, transpeptidase) Peptidoglycan biosynthesis

 Peptidoglycan : unique in bacteria Targets for antibiotics  β-lactams Inhibition of cross-link formation Bind to penicillin-binding protein (transpeptidase)  cycloserine (4-amino-3-isoxazolidinone, seromycin) a cyclic analogue of D-alanine Inhibit alanine racemase & D-alanine:D-alanine ligase Inhibit peptide formation in the cytosolic stage Effective against Mycobacterium tuberculosis

 Bacitracin a mixture of related cyclic peptides Interferes with the dephosphorylation of bactoprenol pyrophosphate Inhibit the transport of monomers across the cell membrane Topical preparation only (highly toxic if used internally)  Vancomycin glycopeptide antibiotic Interact with the terminal D-Ala-D-Ala moieties of the NAM/NAG-peptides Prevent the formation of long polymers & cross-linking methicillin-resistant S. aureus (MRSA) severe Clostridium difficile colitis

대사조절 (Metabolic control)  생물체는 항상 변화하는 환경에 적응하여 주어진 조건에서 가장 효율적으로 생존하고 증식함  대사조절 (coordination of metabolism). 세포는 필요한 물질들만, 필요할 때에, 필요한 양만 합성. 세포는 다양한 방법으로 대사경로를 구성하는 생화학 반응들의 속도 조절  중요한 대사조절 방법. 효소의 합성 조절 ( 유전자의 발현 조절 ). 효소의 분해 조절. 효소의 활성 조절. 세포의 투과성 조절