AMINO ACID DERIVED BIOMOLECULES Flashcards
State the amino acid derived compound abundant in the muscle
Creatine phosphate
Explain the biosynthesis and degradation of creatine phosphate.
- Creatine is produced from arginine and glycine.
- S- adenosylmethionine (SAM) act as the cofactor.
- Conversion of creatine phosphate is catalysed by the creatine kinase.
- In a normal condition, the creatine will be converted to creatinine that is catalysed by the non enzymatic.
- However, the presence creatine kinase indicates that the muscle is damage.
- The level of creatine kinase is increased in myocardial infarction.
- Creatine and creatine phosphate spontaneously degrades at slow but constant rate to creatinine.
- Creatinine will be excreted out through the urine.
- The amount of creatinine excreted out is proportional to the amount of creatine phosphate which also equal to the total muscle mass.
- If the amount of total muscle mass decreased due to malnutrition, paralysis, or muscular dystrophy, the amount of creatinine excreted out through the urine will be decreased as well.
- Creatinine excretion is impaired in kidney failure.
State the relationship between the level of creatinine and muscle mass
The level of creatinine excreted out through urine is proportional to the amount of creatine phosphate which also proportional to the total mass body.
State the amino acid precursors, one enzyme, and cofactors for the synthesis of creatine phosphate.
Precursors: Glycine and arginine
Enzyme: Creatine kinase
Cofactors: S- adenosylmethionine (SAM)
Briefly describe S-adenosylmethionine (SAM) including its precursor amino acid, function and give examples of biomolecules that require SAM as cofactor (other than creatine phosphate) during the synthesis.
- SAM is cofactor that is produced from the combination of methionine and ATP.
- The function of SAM is to transfer the methyl group to precursors that form several compounds.
- As for example, SAM is needed in phophatidylcholine, epinephrine, melatonin, methylated nucleotides and methylated DNA.
- When SAM transfer the methyl group, SAM will then be converted to SAH or also known as S- adenosyl- homocysteine.
- Then SAH will be converted to homocysteine.
- This homocysteine is needed to regenerate methionine to form cysteine.
State the thyroid hormones and their precursor amino acid.
Thyroid hormones: Thyroxine (T4) and Triiodothyronine (T3)
Precursors: Thyroglobulin for T4 and Tyrosine for T3
State the function of thyroid hormones
- Increases the metabolic rate
- In carbohydrates, it increases the process of glycolysis in the liver.
- Thyroid hormones also help in hepatic glucose production by increasing the sensitivity of the hepatocytes to the gluconeogenic and glycogenolytic actions of epinephrine.
- in protein, it increases the protein synthesis in muscle through its stimulatory effects on the gene expression
- In lipid, it increased the hepatic cholesterol and TG synthesis and conversion of cholesterol to bile salt.
Discuss the synthesis of thyroid hormones.
- The synthesis of thyroid hormones happened in the follicular lumen and follicular cell.
- The iodide (I-) from the blood will transport into the follicular cell through the iodide- trapping mechanism which require symport with sodium.
- In the cell, the I- is oxidised to form I+ and it is catalysed by the thryoid peroxidase.
- In the cell, there is thyroglobulin which contain thyrosine.
- The thyroglobulin is transport into the follicular lumen.
- I+ react with the thyroglobulin to form MIT and DIT.
- The coupling of MIT and DIT will form T3.
- However, the coupling of 2 DITs will form T4.
- T3 and T4 will be stored as amino acid in the thyroglobulin.
- The thyroglobulin is endocytosed.
- Hence, the T3 and T4 is transport back into the follicular cell.
- In the follicular cell, the thyroglobulin undergoes lysosomal degradation.
- This causes, the T3 and T4 including MIT and DIT to be released.
- T3 and T4 will be transported into the blood as hormone.
- While, MIT and DIT will be reused back to form another hormone in the follicular cell.
State the amino acid precursors of any other three hormones in our body
Epinephrine, dopamine, norepinephrine = tyrosine
Melatonin, serotonin = trytophan
Nitric oxide = arginine
State what will happen if the amount of thyroid hormone is low.
- Low metabolic rates
- Decreased heat generation
- Always feeling cold
- Reduce energy expenditure
State what will happen if the amount of thyroid hormone in the body is high.
- High metabolic rate
- High heat generation
- High energy expenditure
- Always feeling hot
- Lose weight
Desc the glutathione synthesis process and state the rate limiting step.
- Glutathione synthesis from the L- glutamate and cysteine to form y- glutamylcysteine by glutamylcysteine synthetase.
- Then y- glutamylcysteine is being added together with the glycine forming glutathione that is catalysed by glutathione synthase.
- The rate limiting step is regulated by cysteine availability.
What is the function of glutathione?
- Glutathione is a reductant to maintain stability of erythrocyte membranes.
- This is from the radicals and H2O2 that are continuously produce as by products of metabolism.
- H2O2 will attack the double bond in phospholipid which causes the cell to become rigid.
- Hence, GSH is important to reduce the H2O2 becoming H2O to prevent the cell membrane from damage.
- Other than that, glutathione also transport amino acid across cell membrane and release into the cell where glutathione will bind to the y- glutamyl transpeptidase forming y- glutamyl amino acid.
- y- glutamyl amino acid will be released within the cell.
- Lastly, the glutathione conjugate with drug to ensure them more water soluble for excretion so it can be excreted out through the urine to prevent high toxicity.
Explain the catabolism of purine.
- Catabolism of purine always happen in the liver.
- AMP is deaminated to IMP and is catalysed by the AMP deaminase.
- IMP and GMP are dephosphorylated and the ribose is cleaved from the base by purine nucleoside phosphorylase.
- Hypoxanthine which is the base produced by the cleavage from the IMP is converted to xanthine by xanthine oxidase.
- While, guanine is deaminated by guanase to xanthine.
- Xanthine is then converted to uric acid by xanthine oxidase.
- High amount of uric acid in the blood will lead to gout.
Explain the biosynthesised of carnithine.
- Biosynthesised of carnithine occur in the liver and kidney
- it starts from lysine
- vitamin C or also known as ascorbic acid is needed in this synthesised of carnithine
- lysine is converted to trimethylysine with the help from S-adenosylmethionine as their cofactor.
- trimethyllysine is then converted to trimethyl- 3- hydroxyllysine. This process need help from Fe3+ and ascorbic acid.
- trimethyl-3- hydroxyllysine is then converted to 4-trimethylaminobutyraldehide.
- 4- trimethylaminobutyraldehide need B3 to convert to 4-trimethylaminobutyrate.
- lastly, 4-trimethylaminobutyrate is then converted to carnithine with the help from the Fe2+ and ascorbic acid.
- In skeletal muscle, the amount of carnithine is really high
- The function of carnithine is to transport fatty acid from cytosol into mitochondria during the breakdown of lipids for the generation of energy.
