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Biologically Active Nitrogenous Products


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

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