Branched Chain Amino Acids, Aromatic Amino Acids etc Flashcards
What is a glucogenic AA?
AA that can be converted to glucose
What are the glucogenic AA’s
All AA’s except leucine and lysine
What is a ketogenic AA?
AA that can make ketone bodies (acetyl Co-A)
What are the ketogenic AA’s?
Leucine and lysine
What are glucogenic AAs that can also produce ketone bodies?
Phenylalanine Isoleucine Threonine Tryptophan Tyrosine
What are the branch chain AAs?
Valine
Isoleucine
Leucine
What are the steps involved in metabolism of branch chain AAs?
- Transamination
2. Oxidative carboxylation by an a-keto acid dehydrogenase
What is maple syrup urine disease?
defect in branch chain a-keto acid dehydrogenase complex
Therefore there is an accumulation of an a-keto acid
What are the characteristics of maple syrup urine disease?
- odor of urine is like maple syrup
- failure to thrive, developmental delay (b/c it affects brain tissue)
What is the therapy for maple syrup urine disease?
low protein diet, low in branched-chain AAs
What is can serine be synthesized from?
glucose (glycolysis intermediate)
What are the major sites of serine synthesis?
liver and kidney
What is one purpose of serine?
Can be used as an energy source by tissues
What can glycine be synthesized from
serine (also threonine which is minor)
What does the pathway for the biosynthesis of glycine involve?
folic acid (CH2 acceptor) and pyridoxal phosphate
What can glycine be converted to?
glyoxylate
What are some molecules that glycine is a precursor of?
Creatine Heme Glutathione purine nucleotides glycochenodeoxycholate (bile salts)
Where does synthesis of creatine begin?
kidney
Where does synthesis of creatine ends?
liver
Some partially synthesized creatine goes to the liver, where does this creatine go?
to other tissues eg heart, skeletal muscle, brain
What is one function of creatine?
source of high energy phosphate to replenish ATP
How is creatinine formed?
non-enzymatically
irreversibly
spontaneously
rate of formation is proportional to muscle mass
How is creatinine excreted?
in urine
What does creatinine levels in the urine tells us?
kidney function
muscle wasting
Maple syrup disease leads to accumulation of:
A. Glucose and fructose in the blood and urine
B. Valine and leucine in the blood and urine
C. Glycine in the blood and urine
D. Alpha-keto acids in the blood and urine
D
Glutamate is a precursor or product of which AAs?
Histidine
Glutamine
Proline
Arginine
What is GABA?
an inhibitory neurotransmitter
What is the precursor of GABA
Glutamate
What is one thing synthesis of GABA requires
Pyridoxal phosphate PLP
What can affect the formation (failure to form) of GABA
low levels of vit B6
How can ornithine form outrescine
by decarboxylating ornithine
How is NO derived?
From the metabolism of arginine
What is the precursor of tyrosine?
Phenylalanine
It is hydroxylated to form tyrosine
What does the formation of tyrosine from phenylalanine requires?
tetrahydrobiopterin (BH4, synthesized in our bodies from GTP)
What defect causes PKU?
defect in phenylalanine hydroxylase (phenylalanine cant be hydroxylated to form tyrosine)
What defect causes Alkaptonuria?
defect in homogentisate oxidase, which causes buildup in homogentistate which darkens urine
What defect causes Albinism?
defect in tyrosinase, inability to synthesize melanin pigment
defect in tyrosine metabolism in melanocytes
Phenylalanine/tyrosine are precursors for
Melanins (pigment molecules)
Neurotransmitters (dopamine norepinephrine, epinephrine)
Tryptophan is a precursor for:
serotonin (neurotransmitter)
melatonin (circadian rhythms)
Classical Phenylketonuria (PKU) results from a defect in phenylalanine hydroxylase. If untreated, this leads to:
A. accumulation of tyrosine in the urine
B. Accumulation of phenylalanine in the urine
C. Accumulation of acetone in the urine
D. Accumulation of phenylacetate in the urine
D
