Amino Acid Metabolism Flashcards
What must occur to proteins before they are absorbed in the intestines, and what enzyme faciliates this reaction?
proteolytic enzyms.
Tripeptides and Dipeptides are broken down by what enzyme before they are released in the blood?
peptidases
What are required for intracellular protein turnover?
proteasomes
In the production of ammonia, an amino group is transferred to what other amino acid?
glutamate
What enzyme transfers an amino acid to glutamate?
aminotransferase
What enzyme involves glutamate and the production of NADH, as well as urea?
dehydrogenase
Where does the urea cycle occur?
The liver
What components of the urea cycle are found in the liver?
carbamoyl phosphate and citrulline
What enzyme helps funnel nitrogens into the urea cycle?
aminotransferase
In the brain, the conversion of alpha ketoglutarate to glutamate is facilitated by what enzyme?
glutamate dehydrogenase
In the brain, the conversion of glutamate to glutamine synthetase is facilitated by what enzyme?
glutamine synthetase
In the brain, alpha ketoglutarate must be converted into what amino acid before it can travel to the bloodstream?
Glutamine
What does the liver convert glutamine into so that it can go into the urea cycle?
ammonium (NH4+)
What enzyme in the liver converts glutamine into glutamate?
glutaminase
What is the purpose of the glucose-alanine cycle?
To remove excess ammonia from the muscles.
It involves converting alanine and glutamate into ammonium.
What are the two major types of reactions that remove nitrogen?
deamination
trans-amination
True or false: only amino acids (di and tripeptides) get into the bloodstream.
true
Does pepsinogen or pepsin break down things in the stomach?
pepsin
What is the role of trypsinogen?
To break down proteins into amino acids.
Proteins can be degraded via two methods. What are they?
lysosomal breakdown
proteosomes
The carbon skeleton from proteins can bue used for what?
cellular respiration.
The first step of the urea cycle is what type of reaction?
trans-amination (transfer of an amino group).
Glutamate is made.
Once amino acids have formed glutamate, what happens to them?
They undergo dehydrogenation to become urea.
What is the rate-limiting step of the urea cycle?
The production of carbamoyl phosphate from ammonium and carbon dioxide.
How is ammonium toxic to the brain?
Because the brain is de-energized when there is an excess amount of ammonia.
Protein breakdown in the muscles helps to regulate the balance of what?
nitrogen
What enzyme converts carbon dioxide into carbamoyl phosphate?
carbamoyl phosphate synthetase I.
What enzyme converts carbamoyl phosphate to citruline?
transcarbamoylase
What enzyme converts citrulline to argininosuccinate?
argininosuccinate synthetase
What enzym converts arginosuccinate into arginate?
arginosuccinate lyase
What enzyme converts arginine to ornithine?
argininase I
What is needed between ornithin and citruline?
An ornithine/citrulline transporter.
What does glucogenic mean?
an amino acid that is capable of making glucose.
What does ketogenic mean?
The ability to make ketones
Where does citro-anemia occur?
Between citrulline and arginosuccinate.
A deficiency in enzymes does what to BUN levels?
Causes BUN levels to decrease.
What is a positive NB?
Amount of nitrogen intake is higher than nitrogen excretion.
What is negative NB?
nitrogen excretion is higher than intake
Is the case in starvation/malnutrition
Where do the amino groups in urea come from?
glutamate and aspartate
What urea cycle intermediate is shuttled into the mitochondria?
ornithine
What enzyme catalyzes the rate-limiting step of the urea cycle?
carbamoyl phosphate synthetase
Heme is a ___ containing compound
Nitrogen
What is the rate determining step of heme synthesis?
the reaction of succinyl CoA and glycine.
What vitamin is required in the first reaction of heme synthesis?
vitamin B6
What is the enzyme used in the rate-determing step?
allosynthase
What organ is affected by acute intermittent porphyria?
The liver
Congenital erythropoietic porphyria has an effect on what?
red blood cells
What protein carries bilirubin in the blood?
albumin
Conjugated bilirubin is associated with what sugar?
diglucuronide
What distinguishes the conjugated and nonconjungated (indirect) bilirubins?
The conjugate rubin is solubule and can be tested in a blood sample. Th nonconjugated (indirect) has to be separated from albumin.
Conjugated bilirubin has the diglucuronide
Histamine is derived from what amino acid?
Histidine
Sphingosine is derived from what amino acid?
serine
Thyroxine is derived from what amino acid?
tyrosine
Epinephrine is derived from what amino acid?
tyrosine
Serotonin is derived from what amino acid?
tryptophan
NAD is derived from what amino acid?
tryptophan
Nitric oxide is derived from what amino acid?
arginine
What cofactor dos nitric oxide need?
BH4
What is nNOS?
neuronal nitric oxide synthase. IT is expressed in neurons and produces nitric oxide as a neurotransmitter.
What is iNOS?
inducable nitric oxide synthase. It is found in the immune system and is a killer compound to bacteria and microorganisms.
What is eNOS?
endothelial-derived nitric oxide synthse. It acts as a vasodilator and is produced in endothelium. It moves through the surrounding muscle and relaxes.
What are porphyrins synthesized from?
glycine and succinyl CoA
What enzyme converts delta-amino levullinate into porphobillnogen?
ALA dehydratase.
It is associated with lead poisoning.
What enzyme converts porphobillnogen into a linear tetrapyrrole?
prophobilinogen deaminase
It is associated with acute intermittent porphyria
What enzme converts a linear tetrapyrrole into uroporphyrinogen III?
uroporphyrinogen III synthase
It is associated with congenital erythropoetic porphyria
What enzyme converts urophyrinogen III into corproporphyrinogen III?
uroporphyrinogen decarboxylase
The heme degradation products (billverdin and Billrubin) are responsible for what?
the color of bruises
What are the degradation products of heme?
billiverdin and billirubin
Glutathione reacts with hydrogen peroxide and organic peroxides. What does this indicate that glutathione is?
an antioxidant
Selenium is important in what system?
The glutathoine system
Protein digestion leads to absorption of what?
amino acids and di (tri) peptides.
