Amino Acids Oxidases Carbon

OUTLINE: Protein Degradation (Catabolism) Fermentations Pyruvate Krebs’ Cycle Oxidative Phosphorylation Amino-Acid Degradation Dealing with the nitrogen Digestion Inside of cells Protein turnover Introduction and review Transport Glycogenolysis Glycolysis Other sugars Pasteur: Anaerobic vs Aerobic Electron transport Chemiosmotic theory: Phosphorylation Fat Catabolism diet storage Fatty acid Catabolism FOUR stages in the catabolism of lipids: Ubiquitin Proteosome Ammonia free transamination ß know mechanism Carbamoyl-phosphate synthetase Urea Cycle 4 Steps Ornithine transcarbamylase Arginino-succinate synthetase Arginino-succinase Arginase Energetics Urea Bi-cycle Dealing with the carbon Mobilization from tissues (mostly adipose) Seven Families 1. ADENQ (Transaminase/deaminase Family) 2. RPH (Glu Family) Activation of fatty acids Oxidase Fatty-acyl CoA Synthetase One-carbon (1-C) metabolism Transport THF carnitine SAM Fates of the 29 Oxidation 3. GSC (Pyruvate Family) Rationale nitrogen atoms in 20 PLP uses Saturated FA 4. MT – 1-C metabolism (a-Ketobutyrate Family) b-oxidation AA: 5. FY – oxidases (Aromatic Family) 4 steps: dehydrogenation 6. KW (a-Ketoadipate Family) hydration 7. VIL (Branched-chain AA Family (BCAA)) oxidation 8. Propionyl-CoA thiolase Nucleic-Acid Degradation energetics 9 ammonia nucleotide to bases Unsaturated FA 18 transamination salvage vs oxidation energetics Odd-chain FA 2 urea purine hormone regulated specific lipases glycerol Ketone Bodies Other organelles pyrimidine Amino Acid Degradation: the carbon “skeletons” A. Concepts 1. Convergent 2. ketogenic/glucogenic The SEVEN 3. Reactions seen before B. Transaminase (A,D,E) / Deaminase (Q,N) Family C. Related to biosynthesis (8) 1.Glu Family (R,P,H) a. b. (7) Families Introduce oxidases/oxygenases Introduce one-carbon metabolism (1C) 2. Pyruvate Family (G,S,C) a. PLP reactions a. 1-C metabolism 3. a-Ketobutyric Family (M,T) D. Dedicated (7) 1. Aromatic Family (F,Y) a. oxidases/oxygenases 2. a-Ketoadipic Family (K,W) 3. Branched-chain Family (V,I,L) E. Convergence with Fatty Acids: propionyl-CoA Before FY 29 N 1 Amino Acid Degradation This is what you need to Know from Lectures 22 & 23 oxidase Hydroxylases & dioxygenases dioxygenase Reductive de-amination Hydroxylases & dioxygenases F,Y Amino Acid Degradation Aromatic Family O2 Phenylalanine hydroxylase NIH-shift H2O Tyrosine aminotransferase PLP 2 4 _ O2 CO2 p-hydroxyphenylpyruvate dioxygenase H –O H –O carbocation 6 N IH -shift Oxidative decarboxylation alpha to a carbonyl ⊕ 7 5 3 8 4 2 1 OO O2 Homogentisate 1,2-dioxygenase Ferryl-peroxyl O 2,4-shift 4 5 6 7 8 3 2 1 O Maleylacetoacetate isomerase Fumarylacetoacetase Succinate Acetoacetyl-CoA H2O Succinyl-CoA 3-ketoacyl-CoA transferase Acetoacetate 2 Amino Acid Degradation: Oxidases Nomenclature Oxidases – use molecular oxygen as an electron acceptor, but no atoms into substrate – e.g., cytochrome oxidase, proline oxidase – usually have water or hydrogen peroxide as product A(red) + O2 + 4H+ à A(ox) + 2H2O Oxygenase* – use of molecular oxygen to put into the substrate – dioxygenases – use both atoms; e.g., cysteine dioxygenase A + O2 à AO2 – mono-oxygenases – one atom in substrate, one atom as water RH + BH2 + O2 à AOH ROH + B + H2O AH • The enzyme is a cytochrome called P-450 • The co-substrate electrons are from NADPH • There is Cytochrome P-450 reductase to funnel electrons from co-substrate (B) *a.k.a.: hydroxylase, mixed-function oxygenase, “mixed-function oxidase” Amino Acid Degradation: Oxidases RH + BH2 + O2 à ROH + B + H2O Hydroxylases Example of P-450 reactions in adrenal gland: 1) Source of reducing electrons are most often NADPH (the co-substrate) 2) Other co-substrates a) FAD, FeS clusters, a-ketoglutarate (oxidative decarboxylation to succinate) b) Others: tetrahydrobiopterin (Phe hydroxylase) 3) Major class are the P-450 heme hydroxlases a) Expressed in liver and adrenal glands b) Steroids & fatty acids c) Xenobiotics (drugs) Called CYP i. Specific ii. Non-specific (CYtochrome P-450) iii. Inducible iv. Drug-drug interactions 3 F,Y Amino Acid Degradation • • • Intermediates of the central metabolic pathway Some amino acids result in more than one intermediate. Ketogenic amino acids can be converted to ketone bodies. Seven to Acetyl-CoA • Leu,7 Ile,7 Thr, Lys,6 Trp,6 Phe,5 Tyr5 Glucogenic amino acids can be converted to glucose. Six to pyruvate3,1 Ala, Cys, Gly, Ser, Thr, Trp Five to a-ketoglutarate Arg, Glu, Gln, His, Pro Four to succinyl-CoA7,4 Ile, Met, Thr, Val Two to fumarate5 Phe, Tyr 2,1 Two to oxaloacetate 1 a-ketobutyric Asp, Asn ✓1Trans-/de-aminase family ✓2Glu family ✓3Pyruvate family ✓4Alpha-keto butyric family ✓5Aromatic family 6Alpha-keto adipic family Branched-chain family 7 Amino Acid Degradation: the carbon “skeletons” A. Concepts 1. Convergent 2. ketogenic/glucogenic The SEVEN 3. Reactions seen before B. Transaminase (A,D,E) / Deaminase (Q,N) Family C. Related to biosynthesis (8) 1. Glu Family (R,P,H) a. b. (7) Families Introduce oxidases/oxygenases Introduce one-carbon metabolism (1C) 2. Pyruvate Family (G,S,C) a. PLP reactions a. 1-C metabolism 3. a-Ketobutyric Family (M,T) D. Dedicated (7) 1. Aromatic Family (F,Y) a. oxidases/oxygenases 2. a-Ketoadipic Family (K,W) 3. Branched-chain Family (V,I,L) E. Convergence with Fatty Acids: propionyl-CoA Before KW 29 N 4 Amino Acid Degradation Amino Acid Degradation K,W a-Ketoadipic Family a-Aminomuconate reductase O Tryptophan 2,3dioxygenase O O N-formyl-L-kynurenine N10-formylTHF Kynurenine formamidase a-Amino muconate esemialdehyde dehydrogenase O Kynurenine hydroxylase 2-Amino 3carboxylmuconate esemialdehyde decarboxylase O Kynureninase Alanine O 2-Amino muconate esemialdehyde O Muconic acid 3-Hydroxyanthranilic acid 3,4-dioxygenase O 5 Amino Acid Degradation a-Ketoadipic Family -removal of e-amino by reductive de-amination; -results in oxidation of e-carbon Lysine:a-ketoglutarate reductase Saccharopine dehydrogenase glutamate ④ 2-aminoadipate aminotransferase a -ketoglutarate PLP a-aminoadipate-d-semialdehyde dehydrogenase Amino Acid Degradation • • • K,W Intermediates of the central metabolic pathway Some amino acids result in more than one intermediate. Ketogenic amino acids can be converted to ketone bodies. Seven to Acetyl-CoA • Leu,7 Ile,7 Thr, Lys,6 Trp,6 Phe,5 Tyr5 Glucogenic amino acids can be converted to glucose. Six to pyruvate3,1 Ala, Cys, Gly, Ser, Thr, Trp Five to a-ketoglutarate Arg, Glu, Gln, His, Pro Four to succinyl-CoA7,4 Ile, Met, Thr, Val Two to fumarate5 Phe, Tyr Two to oxaloacetate1 Asp, Asn 2,1 [F,Y] [K,W] a-ketoadipic a-ketobutyric ✓1Trans-/de-aminase family ✓2Glu family ✓3Pyruvate family ✓4Alpha-keto butyric family ✓5Aromatic family ✓6Alpha-keto adipic family 7 Branched-chain family 6 Amino Acid Degradation: the carbon “skeletons” A. Concepts 1. Convergent 2. ketogenic/glucogenic The SEVEN 3. Reactions seen before B. Transaminase (A,D,E) / Deaminase (Q,N) Family C. Related to biosynthesis (R,P,H; C,G,S; M,T) 1. Glu Family a. b. (7) Families Introduce oxidases/oxygenases Introduce one-carbon metabolism (1C) 2. Pyruvate Family a. PLP reactions a. 1-C metabolism 3. a-Ketobutyric Family (M,T) D. Dedicated 1. Aromatic Family (F,Y) a. oxidases/oxygenases 2. a-Ketoadipic Family (K,W) 3. Branched-chain Family (V,I,L) E. Convergence with Fatty Acids: propionyl-CoA Before VIL 29 N Amino Acid Degradation 7 V,I,L Amino Acid Degradation • Degradation of branched-chain amino acids does not occur only in the liver • Leucine, isoleucine, and valine are oxidized for fuel in muscle, adipose tissue, the kidneys, and the brain • Branched-chain amino acids are degraded to succinyl-CoA, an important citric acid cycle intermediate, and acetyl-CoA, an important fuel molecule 7 st eps CO2 3 steps 5 steps Ketone Bodies HMG-CoA 6 Isoprene biosynthesis CO2 5 4 3 2 1 b-Hydroxy-methyl-glutaryl-CoA (OMSGAP) Amino Acid Degradation Alanine Cysteine Glycine Serine Pyruvate Glutamate Glutamine Histidine Proline Arginine Methionine Threonine a-Ketoglutarate OXIDATIVE DECARBOXYLATION V,I,L Acetyl-CoA pyruvate dehydrogenase com plex Dehydrogenase (FAD) Hydratase (H2 O) Succinyl-CoA a -ketoglutarate dehydrogenase com plex Dehydrogenase (NAD+ ) Thiolase (CoASH) a-Ketobutyrate Propionyl-CoA 2 Hydrolase (CoASH) 2 Carboxylase (biotin) a-Ketoadipate Glutaryl-CoA 2 2 2 Crotonyl-CoA 2Acetyl-CoA Crotonyl-CoA | – CO O 2 | – CO O biotin Glutaconcyl-CoA CO2 CoASH a-Ketoisovalerate Methyl malonyl-CoA || O OH a-Keto b-methylvalerate PLP a-Keto isocaproate CoASH Isobutryl-CoA TPP FAD Lipoic acid a-Methybutryl-CoA OH Branched-chain a-keto acid dehydrogenase complex || O Lysine Tryptophan KEY a-methylacetoacetyl-CoA CO2 Acetyl-CoA + Propionyl-CoA Isovaleryl-CoA CH2 OH Biotin HMG-CoA 8 Amino Acid Degradation • • • Intermediates of the central metabolic pathway Some amino acids result in more than one intermediate. Ketogenic amino acids can be converted to ketone bodies. Seven to Acetyl-CoA • V,I,L Leu,7 Ile,7 Thr, Lys,6 Trp,6 Phe,5 Tyr5 Glucogenic amino acids can be converted to glucose. Six to pyruvate3,1 Ala, Cys, Gly, Ser, Thr, Trp Five to a-ketoglutarate Arg, Glu, Gln, His, Pro Four to succinyl-CoA7,4 Ile, Met, Thr, Val Two to fumarate5 Phe, Tyr Two to oxaloacetate1 Asp, Asn 2,1 [F,Y] [K,W] a-ketoadipic ✓1Trans-/de-aminase family ✓2Glu family ✓3Pyruvate family ✓4Alpha-keto butyric family ✓5Aromatic family ✓6Alpha-keto adipic family ✓7Branched-chain family a-ketobutyric propionylCoA Amino Acid Degradation Same Complex 9 Clinical Correlations Genetic Defects in Aromatic Family Degradation Lead to Disease ⊕ ⇀ Alkaptonuria Albinism ⊕ DOPAmine • In phenylketonuria (PKU) there is a buildup of Phe and phenylpyruvate • In Tyrosinemias there a multiple symptoms with severity increasing from III àII à I – – Impairs neurological development leading to severe intellectual deficits Controlled by limiting dietary intake of Phe – – Impairs neurological development leading to severe intellectual deficits Controlled by limiting dietary intake of Phe • In Alkatonuria there is a buildup of homogentisate, which turns black on oxidation 10