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61 Cards in this Set
- Front
- Back
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When is creatine phosphate formed, when [ATP] is high or low?
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High
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Why don't we just store more ATP?
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they are important effectors of enzymes
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Where does biosynthesis of creatine phospate occur?
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Kidney then liver
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What part of the creatine pathway occurs in the kidney and which in the liver?
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a) kidney: Glycine + arginine -> Guanidinoacetate… b) Liver: Guanidinoacetate + 1 Carbon unit (from SAM) -> Creatine + ATP (+ creatine kinase) -> creatine phosphate
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What is the most common use of AdoMet (SAM)?
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methylation of guanidinoacetate in the formation of creatine
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What is needed to form creatine?
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glycine, arginine, methionine (
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Why is it that creatine phosphate has so great a negative ∆G° kcal/mol?
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the resonance structure is stable and renders the phosphate a good leaving group.
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Why is ATP a good energy compound? Why is creatine phosphate a good storage buffer for ATP?
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a) it's a good intermediate between high and low energy phosphorylated compounds. b) because it is metabolically isolated from all other transfer potential compounds except ATP
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What purpose does nitric oxide play?
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it is a vasodilator and neurotransmitter
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Which drug can produce nitric oxide in angina patients?
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nitroglycerine
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What effect does NO have on smooth muscle?
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relaxes it
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What is the precursor for NO?
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arginine
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a) What is required to produce NO from agrinine... b) and what else is produced?
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a) NO synthase, THB, NADPH, Oxygen… b) citrulline
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What is NO synthase like, in that it uses molecular oxygen and THB (BH4)?
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Phenylalanine hydroxylase (PAH)
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What do the following do with arginine? Kidney, liver, neurons
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Kidney: makes guanidinoacetate (creatine phosphate precursor)… Liver: breaks down arginine with arginase to make urea… Neurons: use arginine to make NO
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What is a polyamine and what is its use?
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positively charged compound that interacts with (sticks to) DNA for synthesis, rapid repair, and chromatin maintenance.
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What are the two main players in polyamine synthesis?
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SAM and ornithine
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What are the other roles for SAM and ornithine?
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SAM: methyl donar… ornithine: handle in urea cycle
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What is the half-life of ornithine decarboxylase? And what cofactor is required for its catalysis of ornithine?
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11 minutes… PLP
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What is the first thing that happens to SAM during polyamine biosynthesis? And what is required?
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decarboxylation… pyruvate
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What is the second thing that happens to SAM during polyamine synthesis?
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the unstable S loses a constiuent: the polyamine group.
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How many SAMs and ornithines are required per polyamine?
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2 SAM + 1 ornithine/ polyamine
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What is the rate limiting step in the biosynthesis of polyamines?
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ornithine decarboxylase, which is regulated by the short half-life of ODC
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Draw the polyamine biosynthesis pathway.
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What is carnitine involved in?
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the transport of FA
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What is the precursor of carnitine? And how is this precursor formed?
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N-Trimethyllysine… b) Lysine + 3 methyl groups are added by transferases and AdoMet
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Where is the lysine derived that fomrs carnitine?
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from the degradation of actin or myosin
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What three reactions are seen over and over again in the biosynthesis of neurotransmitters?
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decarboxylation, hydroxylation, and methylation
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What is a hydroxylation?
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addition of an -OH group
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Name 8 neurotransmitters
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histamine, epi, norepi, glycine, glutamine, GABA, Serotonin, and dopamine
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what effect does histamine have on smooth muscle
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It is a NT, it causes S. muscle contraction
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How is histamine synthesized and is required?
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decarboxylation of histidine in the presence of histidine decarboxylase and PLP
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What vitamin is PLP associated with?
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B6
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How is the activity of PLP similar in transamination and decarboxylation?
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the amino acid attaches to the coenzyme, creating a Schiff base linkage
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How is the activity of PLP different in transamination and decarboxylation?
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in transamination the keto-acid would depart leaving the Nitrogen… in decarboxylation, PLP is an electron sink and promote the leaving of the carboxyl group.
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What pathway does GABA evolve from?
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TCA
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Where does the GABA shunt occur and what is required?
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at the ∂-KG --> glutamate… PLP is require along with the transaminase.
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What function does PLP serve in the formation and breakdown of GABA?
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transamination, decarboxylation, transamination again
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Where is GABA reclaimed by the TCA cycle?
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succinate
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a) What does vigabatrin... b) treat? What does vigabatrin do?
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a) seizures… b) It inhibits GABA transamination, thus GABA degradation is inhibited
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Name 3 catacholamines (1,2-benzenediol)
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epi, norepi, dopamine
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How are Dopa and L-Dopa similar
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they are the same thing
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What is the precursor for catacholamines?
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phenylalanine
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In the formation of catacholamines, in the first two reaction that form Dopa, through hydroxylation, what is required?
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BH4 (THB)
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In the formation of catacholamines, what is required to form dopamine from dopa in a decarboxylation rxn?
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PLP
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In the formation of catacholamines, what is required to form norepinephrine from dopamine in a hydroxylation rxn?
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Vit C
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What is required to form epinephrine from norepinephrine in a methylation rxn?
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SAM and methltransferase, in the addition of a methyl group
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Parkinson's disease is caused by the substantia nigra's inability to make dopamine. How is this treated?
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Since dopamine cannot cross the blood brain barrier, L-Dopa is given orally, along with a intestinal decarboxylase inhibitor: "Carbidopa"
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What two compounds are needed for the degradation of catacholamines?
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MAO and COMT
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What does MAO do?
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Monoamine oxidase (removes an amine group)
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What does COMT do?
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transfers a methyl group using SAM
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How do MAO inhibitors work? And what is the clinical relevance?
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The competitively inhibit MAO, and thus catacholamine breakdown is inhibited… b) it is an antidepressant that works by preventing NT degradation
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What Iproniazid and what is/was used for?
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originally used as an antibiotic for TB… it is a MAO inhibitor for depression.
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a) What is serotonin formed from? b) What is it degraded to and what is responsible for serotonin's degradation?
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a) tryptophan… b) 5-hydroxy-indoleacetic acid… MAO
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How do you assess serotonin levels in the body?
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check 5-hydroxy-indoleacetic acid levels
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Which amino acids largely compose collagen?
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33%-Gly, 21%-Pro or Hydroxyproline
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In collagen, what cofactor promotes hydroxylation?
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vit-C
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What role do hydroxyprolines and hydroxylysine play in collagen?
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a) Hydroxyproline: stabilize right-handed superhelix… b) hydroxylysine: used to attach carbohydrates
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What condition is associated with vitamin C deficiency?
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scurvy
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How are right-handed stabilized?
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crosslinks between left-handed superhelices extracellularly
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Name the 3 branched chained amino acids
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Val, Ile, Leu
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