Amino Acids Flashcards
amino acids
building blocks of proteins
basic chemical structure of amino acid
one amino group and one carboxyl functional group
alpha-carbon
N-terminal end and C-terminal end are bonded to this carbon.
peptide bond
linkage of the amino group of one amino acid to the carboxyl group of another amino acid
polypeptide
chain of amino acids linked by peptide bonds
protein
large polypeptide
size of proteins in serum
100-150 amino acids in length
essential amino acids- require dietary supplement
arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine
nonessential amino acids-not required dietary supplement
alanine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, and tyrosine
how much of total required daily energy do proteins provide
20%
what are the ketogenic amino acids
isoleucine, leucine, lysine, phenylalanine, tryptophan, tyrosine, and threonine
what are the glycogenic amino acids
alanine, arginine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, phenylalanine, tryptophan, tyrosine, and threonine, isoleucine, valine, histidine, proline, methionine,
Role(s) of arginine
cell division, wound healing, stimulation of protein synthesis, immune function, release of hormones, and in conversion of ammonia to urea for excretion
Role(s) of histidine
grow and repair of body tissues, maintain myelin sheaths around nerve cells, precursor to histamine (immune response), manufacturing of red and white blood cells, protection from heavy metal toxicity, and source of carbon for synthesis of purine for DNA and RNA
Role(s) of isoleucine, leucine, and valine
branched chain amino-acids; promote healing of muscle tissue, skin, and bones; regulation of blood glucose levels; maintain energy levels; isoleucine in hemoglobin formation; leucine in infant growth; leucine and valine in nitrogen balance in adults
Role(s) of lysine
production of antibodies; lowering triglyceride levels; absorption and conservation of calcium; formation of collagen
Role(s) of methionine
initiation of translation of mRNA (first amino acid incorporated into N-terminal position of all amino acids); source of sulfur for metabolism and growth; breakdown of fats; detoxification of lead and other heavy metals; decrease muscle weakness and prevents brittle hair; reacts with ATP
Role(s) of phenylalanine
promotes alertness and vitality; elevates mood; decreases pain; aids in memory and learning; treatment for arthritis and depression; used by brain to produce norepinephrine; can interfere with serotonin production; direct precursor to tyrosine
Role(s) of threonine
formation of collagen, elastin, and tooth enamel
Role(s) of tryptophan
precursor for serotonin, melatonin, and niacin; natural relaxant; treatment of migrants, weight control, hyperactivity
Role(s) of alanine
product of DNA/dipeptide (anserine and carnosine) breakdown; transfers nitrogen from peripheral tissues to liver for processing and excretion; strengthens immune system through antibody production; reduces buildup of toxic substances when muscle protein is broken down quickly
Role(s) of asparagine
derived from aspartic acid and ATP; transport of nitrogen; requisite amino acid for nervous system; synthesis of ammonia; conversion of amino acids through amination or transamination
Role(s) of aspartic acid
aka aspartate; precursor or asparagine, arginine, lysine, methionine, threonine, isoleucine; metabolite in citric acid cycle and urea cycle; participation in gluconeogenesis
Role(s) of cysteine
potentially toxic; absorbed as cystine; important structural and functional component of proteins
Role(s) of glutamic acid
aka glutamate; precursor to glutamine; neurotransmitter; dysregulation leads to epileptic seizures; metabolism of fats and sugars; transport of potassium in to spinal fluid
Role(s) of glutamine
precursor to proline; renal maintenance of acid-base balance; fuel for health digestive tract; basis of building blocks for synthesis or RNA and DNA; transport of ammonia to liver for metabolism
Role(s) of glycine
synthesis of nucleic acids, bile acids, proteins, peptides, purines, ATP, porphyrins, hemoglobin, glutathione, creatine, bile salts, glucose, glycogen, and other amino acids; detoxification of compounds in liver; inhibitory neurotransmitter in CNS; metal complexing agent; retards muscle degeneration
Role(s) of proline
precursor to hydroxyproline (needed for tendons, collagen, ligaments, and cardiac tissue); wound healing; works with vitamin C to promote healthy connective tissues
Role(s) of serine
precursor to glycine; metabolism of lipids and fatty acids; synthesis of pyrimidines, purines, creatine, and porphyrins
Role(s) of tyrosine
precursor to adrenal hormones (epinephrine, norepinephrine, and dopamine) and thyroid hormones (thyroxine); overall metabolism; function of adrenal glands, thyroid, and pituitary glands; mood elevator
Selenocysteine
21st amino acid; not coded for in genetic code; coded for in stop codon UGA
Pyrrolysine
22nd amino acid; coded for in stop codon UAG; not present in humans
Aminoacidopathies
class of inherited errors of metabolism in which there is an enzyme defect that inhibits the body’s ability to metabolize certain amino acids
Phenylketonuria
PKU; autosomal recessive; 1 in 15,000 births; classic PKU- absence of phenylalanine hydroxylase (PAH) activity increases phenylalanine >1200 micromol/L, which causes brain damage; causes urine to have musty odor; mild PKU is partial deficiency of PAH activity with phenylalanine between 600-1200 micromol/L;
Normal phenylalanine in blood in infants
<120 micromol/liter; <2 mg/dL
Symptoms of PKU
retarded mental development; microcephaly
Hyperphenylalaninemia
phenylalanine elevation between 180-600 micromol/L without phenylketone elevation; deficiency in enzymes needed for regeneration and synthesis of BH4 (1-5% of all cases)
PKU treatment
early detection, diet with low levels of phenylalanine (infant and mom)
Tetrahydrobiopterin (BH4)
cofactor required for enzymatic hydroxylation of phenylalanine, tyrosine, and tryptophan; deficiency leads to elevation of phenylalanine and deficient production for neurotransmitters from tyrosine and tryptophan
PKU detection
Guthrie test, HPLC, HPLC-MS/MS, microfluorometric assay of dried blood filter disks; GC-MS;
Guthrie Test
semiquantitative, bacterial inhibition assay; sensitivity is 180 micromol/L (3mg/dL); blood is placed on agar dish that contains inhibitor of bacterial growth; if phenylalanine is present, inhibitor is overcome and bacteria grow
Microfluorometric assay
quantitative; based on complex formed with phenylalanine and ninhydrin which causes fluorescence
GC-MS
microwave assisted silylation; blood is rapidly derived with N,O, bis(trimethylsilyl)-trifluoroacetamine under microwave irradiation; analyzed by GCMS; confirmation method
Tyrosinemia
autosomal recessive; metabolic disorder of tyrosine catabolism; elevated tyrosine in blood and elevated succinylacetone (toxic metabolite formed when tyrosine cannot be metabolized) by MS/MS; low protein diet required
Alkaptornuria
autosomal recessive; 1 in 250,000 births; mutation in homogentisate oxidase (HGD) gene; required for metabolism of phenylalanine and tyrosine; elevated concentrations of homogentisic acid (HGA) in blood; symptoms present in 3rd decade of life; dark-blue/black pigmentation of of ears, nose, and tendons; small dark spots on sclera of eye; cause arthritis-like degeneration; urine mixed with air will result in brownish-black color due to oxidation of HGA; high dose Vitamin C
Maple Syrup Urine Disease
autosomal recessive; 1 in 185,000 births; absence or reduced activity of branched-chain alpha-ketoacid decarboxylase (BCKD); inhibits metabolism of leucine, isoleucine, and valine; maple syrup or burnt sugar smell of urine, breath, and skin; symptoms in infants include lethargy, vomiting, lack of appetite, and failure to thrive within 1 week of birth; dietary restriction of proteins; leucine concentration of >4mg/dL
Isovaleric Acidemia
1 in 250,000 births in US; mutation in isovaleryl-CoA dehydrogenase (IVD) gene; may be asymptomatic; distinctive odor of sweaty feet; may include failure to thrive, vomiting, lethargy; severe forms can result in permanent brain damage, nervous system damage, and death; protein restrictive diet and supplementation with glycine and carnitine
Homocystinuria
autosomal recessive, 1 in 200,00 births; mutations in CBS, MTHFR, MTR, MTRR, and MMADHC genes; most common is mutation in CBS gene; Guthrie test; symptoms include nearsightedness, dislocation of the lens in the eye, mental retardation, osteoporosis; methionine >2mg/dL
Citrullemia
urea cycle disorder; autosomal recessive
Argininosuccinic aciduria
autosomal recessive; urea cycle disorder; 1 in 70,000 births; lack enzyme argininosuccinic acid lyase (ASL); nitrogen accumulates in blood (ammonia); clinical symptoms start within a few days of life with lethargy and unwillingness to eat; high caloric protein restrictive diet, arginine supplement
Cystinuria
autosomal recessive; 1 in 10,000 births; mutation in SLC3A1 and SLC7A9 genes; elevated levels of cystine (also lysine, arginine, and ornithine); kidney stones, ureters, or bladder stones; other symptoms of hematuria, flank pain, urinary tract infections; increase of fluid uptake or penicillamine; diagnosed by cyanide nitroprusside which produces a red-purple color
Type II citrullinemia
mutation in SLC25A13 gene, which encodes for production of the protein citrin (transports molecules inside cell that are used in production and breakdown of simple sugars, etc); cells are prevented from making citrin, inhibits urea cycle; elevation of ammonia and other toxic substances; confusion, restlessness, memory loss, personality changes, seizures, and coma; high caloric, protein restrictive diet; arginine supplement
Methods of analysis-amino acids
blood drawn after 6-8 hours of fasting; collected in heparin tube and plasma removed immediately; hemolysis and contamination with white blood cells is unacceptable; deproteinization is performed within 30 min of sample collection and analysis performed immediately or sample stored below -20C; urine amino acids is performed on random specimen for screening and 24 hour urine for quantitative measurement
Methods of analysis-amino acids
blood drawn after 6-8 hours of fasting; collected in heparin tube and plasma removed immediately; hemolysis and contamination with white blood cells is unacceptable; deproteinization is performed within 30 min of sample collection and analysis performed immediately or sample stored below -20C; urine amino acids is performed on random specimen for screening and 24 hour urine for quantitative measurement-preserved with thymol; TLC is method of choice- can be 1 or 2 dimensional- stained with ninhydrin to visualize; ion-exchange chromatography with fluorescence detection; LC-MS/MS
normochromic normocytic anemia
type of anemia in which the circulating RBCs are the same size (normocytic) and have a normal red color (normochromic)
