2. What are AMINO ACIDS ?
Amino acids are the building blocks of proteins. The precise amino
acid content, and the sequence of those amino acids, of a specific
protein is determined by the sequence of the bases in the gene that
encodes that protein.
The chemical properties of the amino acids of proteins determine the
biologic activity of the protein. Proteins catalyze almost all of the
reactions in living cells, controlling virtually all cellular processes
Growth, repair, and maintenance of all cells are dependent on amino
acids.
3. BASIC STRUCTURE OF AMINO ACIDS
An amino acid contains at least one of both amino and carboxylic acid
functional groups. The N-terminal end amino group (–NH2) and the C-
terminal end carboxyl group (–COOH) bond to the alpha-carbon with the
amino group of one amino acid linking with the carboxyl group of another,
forming a peptide bond .
A chain of amino acids is known as a polypeptide, and a large polypeptide
constitutes a protein. In human serum, proteins average about 100–150
amino acids in the polypeptide chains. Amino acids differ from one another
by the chemical composition of their R group (side chains).
5. PEPTIDE BOND FORMATION
A peptide bond is a chemical bond formed between two molecules when the
carboxyl group of one molecule reacts with the amino group of the other
molecule, releasing a molecule of water (H2O). This is a dehydration
synthesis reaction (also known as a condensation reaction), and usually occurs
between amino acids.
6.
7. ESSENTIAL /NON-ESSENTIAL AMINO ACIDS
ESSENTIAL AMINO ACIDS:
About half of the 20 amino acids needed by humans cannot be synthesized at
a rapid enough rate to support growth; they must be supplied in food. These
nutritionally essential amino acids must be supplied by the diet in the form of
proteins.
The essential amino acids are arginine (often called semi essential as it is
required for the young but not for adults and can be synthesized in high
enough amounts that the body needs), histidine, isoleucine, leucine, lysine,
methionine, phenylalanine, threonine, tryptophan, and valine.
8. CONT..
NON-ESSENTIAL AMINO ACIDS:
The 10 amino acids that the body can produce are alanine,
asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine,
proline, serine, and tyrosine. Tyrosine is produced from
phenylalanine, so if the diet is deficient in phenylalanine, tyrosine
will be required as well.
Humans do not have all the enzymes required for the biosynthesis of
all of the amino acids.
9. PRODUCTION OF AMINO ACIDS
Under normal circumstances, proteolytic enzymes, such as pepsin and
trypsin, completely digest dietary proteins into their constituent
amino acids. Amino acids are then rapidly absorbed from the intestine
into the blood and subsequently become part of the body’s pool of
amino acids.
Amino acids are also released by the normal breakdown of body
proteins.
10. FUNCTIONS OF AMINO ACIDS
The primary purpose of amino acids is for the synthesis of body proteins,
including plasma, intracellular, and structural proteins.
Amino acids are also used for the synthesis of nonprotein nitrogen-
containing compounds such as purines, pyrimidines, porphyrins,
creatine, histamine, thyroxine, epinephrine, and the coenzyme NAD.
In addition, protein provides 12%–20% of the total daily body energy
requirement.
11. CONT…
The amino group is removed from amino acids by either deamination or
transamination. The resultant ketoacid can enter into a common
metabolic pathway with carbohydrates and fats.
Glucogenic amino acids generate precursors of glucose, such as
pyruvate or a citric acid cycle intermediate. Examples include alanine,
which can be deaminated to pyruvate; arginine, which is converted to
alpha-ketoglutarate; and aspartate, which is converted to oxaloacetate.
Ketogenic amino acids generate ketone bodies. They are degraded to
acetyl-CoA or acetoacetyl-CoA (e.g., leucine or lysine), with some
amino acids being both ketogenic and glucogenic. The ammonium ion
that is produced during deamination of the amino acids is converted
into urea via the urea cycle in the liver.
15. 1. ARGININE ( Arg, R )
Essential amino acid
Arginine is a complex amino acid that is often found at the catalytic
(active) site in proteins and enzymes due to its amine-containing side
chain.
Arginine plays an important role in cell division, the healing of wounds,
stimulation of protein synthesis, immune function, and the release of
hormones.
Arginine is required for the generation of urea, which is necessary for
the removal of toxic ammonia from the body and is also required for the
synthesis of creatine, which degrades to creatinine, a waste product that
is cleared from the body by the kidney.
16. 2. HISTIDINE ( His,H )
Essential amino acid
Histidine is one of the basic (by pH) amino acids due to its imidazole side
chain.
It is the direct precursor of histamine, one of the proteins involved in the
immune response.
Histidine is also an important source of carbon atoms in the synthesis of
purines, one of the two groups of nitrogen bases that make up DNA and RNA.
Histidine is needed to help grow and repair body tissues and to maintain the
myelin sheaths that protect nerve cells. It also helps manufacture red and
white blood cells and helps to protect the body from heavy metal toxicity.
Histamine stimulates the secretion of the digestive enzyme gastrin and acts
as a catalytic site in certain enzymes.
17. 3.ISOLEUCIN ( Ile, I )
Essential amino acid
Isoleucine is in the group of branched-chain amino acids that are
needed to help maintain, heal, and repair muscle tissue, skin, and
bones.
Isoleucine is needed for hemoglobin formation, and it helps to
regulate blood glucose levels and maintain energy levels.
18. 4. LEUCIN ( Leu, L )
Essential amino acid
Leucine is also in the group of branched-chain amino acids, along with valine
and isoleucine.
Leucine is the second most common amino acid found in protein beside
glycine.
Leucine, in conjunction with valine and isoleucine, boosts the healing of
muscle, skin, and bones; aids in recovery from surgery; and lowers blood
glucose levels.
Leucine is necessary for the optimal growth of infants and for nitrogen
balance in adults.
19. 5. LYSINE ( Lys, K )
Essential amino acid
Lysine has a net positive charge, which makes it one of the three basic (by
charge) amino acids.
Lysine plays a role in the production of antibodies and lowers triglyceride
levels.
Lysine is needed for proper growth and bone development in children and to
maintain a proper nitrogen balance in adults.
Lysine helps in the absorption and conservation of calcium and plays an
important role in the formation of collagen, a component of cartilage and
connective tissue.
20. 6. METHIONINE ( Met, M )
Essential amino acid
Methionine is an important amino acid that helps to initiate translation of
messenger RNA by being the first amino acid incorporated into the N-terminal
position of all proteins.
Methionine is a source of sulfur, required by the body for normal metabolism
and growth.
Methionine assists the breakdown of fats, helps to detoxify lead and other
heavy metals, helps diminish muscle weakness, and prevents brittle hair.
Methionine reacts with adenosine triphosphate to contribute to the synthesis
of many important substances, including epinephrine and choline.
21. 7. PHENYALANINE ( Phe, F )
Essential amino acid
Phenylalanine is classified as a nonpolar amino acid because of the hydrophobic
nature of its benzyl side chain.
It promotes alertness and vitality, elevates mood, decreases pain, aids memory and
learning, and is used to treat arthritis and depression.
Phenylalanine is used by the brain to produce norepinephrine, a neurotransmitter
that transmits signals between nerve cells.
Phenylalanine uses an active transport channel to cross the blood-brain barrier and,
in large quantities, interferes with the production of serotonin, another
neurotransmitter.
Phenylalanine is part of the composition of aspartame, a common sweetener used in
prepared foods as a sugar replacement.
Phenylalanine plays a key role in the biosynthesis of other amino acids.
22. 8. THREONINE ( Thr, T )
Essential amino acid
Threonine is an alcohol-containing amino acid that is an important component
in the formation of protein, collagen, elastin (a connective tissue protein),
and tooth enamel.
It is also important in the production of neurotransmitters and health of the
nervous system.
Threonine helps maintain proper protein balance in the body and it aids liver
function, metabolism, and assimilation.
23. 8. TRYPTOPHAN ( Trp, W )
Essential amino acid
Tryptophan is formed from proteins during digestion by the action of
proteolytic enzymes.
Tryptophan is also a precursor for serotonin and melatonin, a neurohormone
and powerful antioxidant.
Tryptophan is a natural relaxant; it helps alleviate insomnia by inducing sleep,
soothes anxiety, and reduces depression.
It is used in the treatment of migraine headaches, aids in weight control by
reducing appetite, and helps control hyperactivity in children.
24. 9. VALINE ( Val, V )
Essential amino acid
Valine is another branched-chain amino acid that is a constituent of fibrous
protein in the body.
Valine is needed for muscle metabolism and coordination, tissue repair, and
maintenance of nitrogen balance. It is used by muscle tissue as an energy
source.
Valine is used in treatments for muscle, mental, and emotional problems;
insomnia; anxiety; and liver and gallbladder disease.
25. 10. ALANINE ( Ala, A )
Non-essential amino acid
Alanine is one of the simplest of the amino acids and is involved in the
energy-producing breakdown of glucose.
Alanine itself is a product of the breakdown of DNA or the dipeptides
anserine and carnosine, and the conversion of pyruvate, a pivotal
compound in carbohydrate metabolism.
Alanine plays a major role in the transfer of nitrogen from peripheral
tissue to the liver, helps in reducing the buildup of toxic substances that
are released into muscle cells when muscle protein is broken down quickly
to meet energy needs, and strengthens the immune system through
production of antibodies
26. 11. ASPARAGINE ( Asn, N )
Non-Essential amino acid
Asparagine was first isolated in 1806 from asparagus juice, naturally,
from where it got its name, becoming the first amino acid to be
isolated.
Asparagine is one of the principal and frequently the most abundant
of the amino acids involved in the transport of nitrogen.
Asparagine is the Beta-amide of aspartic acid synthesized from
aspartic acid and adenosine triphosphate (ATP).
The main function of asparagine is converting one amino acid into
another via amination, the process by which an amine group is
introduced into an organic molecule, and transamination, the reaction
when an amino acid is transferred to an alpha-ketoacid. Asparagine is
required by the nervous system and plays an important role in the
synthesis of ammonia
27. 12. ASPARTIC ACID ( Asp, D )
Non-Essential amino acid
Aspartic acid is alanine with one of the beta hydrogens replaced by a
carboxylic acid group.
Aspartic acid plays a vital role in metabolism during construction of other
amino acids and metabolites in the citric acid cycle. Among the amino acids
that are synthesized from aspartic acid are asparagine, arginine, lysine,
methionine, threonine, isoleucine, and several nucleotides.
Aspartic acid is also a metabolite in the urea cycle and participates in
gluconeogenesis, the generation of glucose from nonsugar carbon substrates.
28. 13. CYSTEIN ( Cys, C )
Cysteine is classified as a nonessential amino acid, but cysteine may be essential for
infants, the elderly, and individuals with certain metabolic diseases or
malabsorption syndromes.
Cysteine is an important structural and functional component of many proteins and
enzymes. Cysteine is named after cystine, its oxidized dimer.
Cysteine is potentially toxic and is catabolized in the gastrointestinal tract and
blood. In opposition, cysteine is absorbed during digestion as cystine, which is more
stable in the gastrointestinal tract. It is cystine that travels to cells, where it is
reduced to two cysteine molecules upon cell entry.
Cysteine is used as a constituent in the food, pharmaceutical, and personal care
industries.
One of its largest applications is in the production of flavors.
29. 14. GLUTAMIC ACID ( Glu, E )
Non-Essential amino acid
Glutamic acid is synthesized from a number of amino acids, and when an amino
group is added to glutamic acid, it forms the important amino acid glutamine.
Glutamic acid is one of the two amino acids that have a net negative charge (by pH),
making it a very polar molecule.
Glutamic acid has been linked to epileptic seizures, is a neurotransmitter, is
important in the metabolism of sugars and fats, and aids transporting potassium into
the spinal fluid.
Glutamic acid is present in a wide variety of foods and is responsible for one of the
five basic tastes of the human sense of taste (umami).
Glutamic acid is often used as a food additive and flavor enhancer in the form of its
sodium salt, monosodium glutamate (MSG).
30. 15. GLUTAMINE ( Gln, Q )
Non-Essential amino acid
Glutamine is the most abundant amino acid in the body, being involved in more
metabolic processes than any other amino acid.
Over 61% of skeletal muscle tissue is glutamine.
Glutamine is converted to glucose when more glucose is required for energy and aids in
immune function.
Glutamine assists in maintaining the proper acid/alkaline balance in the body, provides
fuel for a healthy digestive tract,6 and is the basis of the building blocks for the
synthesis of RNA and DNA.
Studies have shown glutamine to be useful in treatment of serious illnesses, injury,
trauma, burns, and cancer treatment–related side effects and in wound healing for
postoperative patients.
Glutamine is also marketed as a supplement used for muscle growth in weightlifting and
bodybuilding.
Glutamine transports ammonia, the toxic metabolic byproduct of protein breakdown, to
the liver, where it is converted into less toxic urea and then excreted by the kidneys.
31. 16. GLYCINE ( Gly, G )
Non-Essential amino acid
Glycine is the simplest amino acid synthesized in the body and is the only amino
acid that is not optically active because it has no stereoisomers (any of a group
of isomers [compounds with the same molecular formula but a different
structural formula] in which atoms are linked in the same order but differ in
their spatial arrangement).
Glycine is essential for the synthesis of nucleic acids, bile acids, proteins,
peptides, purines, ATP, porphyrins, hemoglobin, glutathione, creatine, bile salts,
glucose, glycogen, and other amino acids.
The liver uses glycine to help in the detoxification of compounds and to help in
the synthesis of bile acids.
Glycine has a sweet taste and is used as a sweetener/taste enhancer.
Glycine is an inhibitory neurotransmitter in the central nervous system (CNS), is
a metal complexing agent, retards muscle degeneration, improves glycogen
storage, and promotes healing.
32. 17. PROLINE ( Pro, P )
Non-Essential amino acid
Proline is the precursor of hydroxyproline, which is manufactured into
collagen, tendons, ligaments, and heart muscle by the body.
Proline is involved in wound healing, plays important roles in molecular
recognition, and is an important component in certain medical wound
dressings that use collagen to stimulate wound healing.
Proline helps in the healing of cartilage and the strengthening of joints,
tendons, and heart muscle, and it works with vitamin C to promote healthy
connective tissues.
33. 18. SERINE ( Ser, S )
Non-Essential amino acid
Serine is the second amino acid that is also an alcohol because of its methyl
side chain, which contains a hydroxy group.
Serine is needed for the proper metabolism of fats and fatty acids and plays
an important role in the body’s synthetic pathways for pyrimidines, purines
(making it important for DNA and RNA function), creatine, and porphyrins.
It is highly concentrated in all cell membranes, is a component of the
protective myelin sheaths surrounding nerve fibers, and aids in the production
of immunoglobulins and antibodies for the maintenance of a healthy immune
system.
34. 19. TYROSINE ( Tyr, Y )
Non-Essential amino acid
Tyrosine is metabolically synthesized from the important amino acid
phenylalanine to become the para-hydroxy derivative of phenylalanine.
Tyrosine is a precursor of the adrenal hormones epinephrine, norepinephrine,
and dopamine and the thyroid hormones, including thyroxine.
It is important in overall metabolism, aiding in the functions of the adrenal,
thyroid, and pituitary glands.
Tyrosine stimulates metabolism and the nervous system, acts as a mood
elevator, suppresses the appetite, and helps reduce body fat, making it useful
in the treatment of chronic fatigue, narcolepsy, anxiety, depression, low sex
drive, allergies, and headaches.
36. AMINOACIDOPATHIES
Aminoacidopathies are a class of inherited errors of metabolism in which
there is an enzyme defect that inhibits the body’s ability to metabolize
certain amino acids.
The abnormalities exist either in the activity of a specific enzyme in the
metabolic pathway or in the membrane transport system for amino acids.
Phenylketonuria (PKU), aminoacidopathy, was the first newborn screening test
introduced in the early 1960s.
Now, some states require screening tests for up to 26 amino acids.More than
100 diseases have been identified that result from inherited errors of amino
acid metabolism. The aminoacidopathy disorders cause severe medical
complications due to the buildup of toxic amino acids and/or byproducts of
amino acid metabolism in the blood
37. 1. Phenylketonuria
Phenylketonuria (PKU) is inherited as an autosomal recessive trait
occurs in about 1 in 15,000 births.
absence of activity of the enzyme phenylalanine hydroxylase (PAH), which
catalyzes the conversion of phenylalanine to tyrosine
In the absence of the enzyme, phenylalanine levels are usually greater than
1200 micro mol/L.
38. CONT…
In the newborn, the upper limit of normal for a phenylalanine level is 120
micro mol/L (2 mg/dL). In untreated classic PKU, blood levels as high as 2.4
mM/L can be found.
Chronically high levels of phenylalanine and some of its metabolites—e.g.,
phenylpyruvic acid, phenylpyruvate (also known as phenylketone), and
phenyllactic acid— can cause significant brain problems.
All of these compounds are found in both the blood and the urine of a PKU
patient, giving the urine a characteristic musty odor. Partial deficiencies of
PAH activity are typically classified as mild PKU if phenylalanine levels are
between 600–1200 micro mol/L or as non-PKU mild hyperphenylalaninemia if
phenylalanine levels are in the range of 180–600 micro mol/L and there is no
accompanying accumulation of phenylketones.
39. CONT..
In infants and children with this inherited defect, retarded mental
development and microcephaly occur as a result of the toxic effects on the
brain of phenylalanine or its metabolic byproducts.
Brain damage can be avoided if the disease is detected at birth and the infant
is maintained on a diet containing very low levels of phenylalanine.
Also, women with PKU who are untreated during pregnancy almost always
have babies who are microcephalic and mentally retarded. The fetal effects
of maternal PKU are preventable if the mother is maintained on a
phenylalanine-restricted diet from before conception through term.
40.
41. 2. Tyrosinemia
The inborn metabolic disorders of tyrosine catabolism are characterized by
the excretion of tyrosine and tyrosine catabolites in urine.
There are three types of tyrosinemia, each with distinctive symptoms and
caused by the deficiency of a different enzyme.
Type I
Type II
Type III
42. Type I Tyrosinemia
Type I tyrosinemiais the most severe form of this aminoacidopathy and is
found in about 1 in 100,000 births.
Type I tyrosinemia is caused by low levels of the enzyme
fumarylacetoacetate hydrolase, the fifth of five enzymes needed to break
down tyrosine.
Symptoms of type I tyrosinemia include failure to thrive, diarrhea, vomiting,
jaundice, cabbage-like odor, distended abdomen, swelling of legs, and
increased predisposition for bleeding.
Type I tyrosinemia can lead to liver and kidney failure, problems affecting the
nervous system, and an increased risk of cirrhosis or liver cancer later in life.
43. Type II Tyrosinemia
Type II tyrosinemia is caused by a deficiency of the enzyme tyrosine
aminotransferase.
Type II tyrosinemia occurs in fewer than 1 in 250,000 births.
Tyrosine aminotransferase is the first in a series of five enzymes that
converts tyrosine to smaller molecules, which are excreted by the kidneys or
used in energy producing reactions.
About half of individuals with type II tyrosinemia are mentally retarded and
have symptoms of excessive tearing, photophobia (abnormal sensitivity to
light), eye pain and redness, and painful skin lesions on the palms and soles of
the feet.
44. Type III Tyrosinemia
Type III tyrosinemia is a rare disorder (only a few cases have been reported)
caused by a deficiency of the enzyme 4-hydroxyphenylpyruvate
dioxygenase.
This enzyme is found mainly in the liver with lesser amounts found in the
kidneys.
It, too, is one of the series of enzymes needed to break down tyrosine.
The clinical picture of type III tyrosinemia patients includes mild mental
retardation, seizures, and periodic loss of balance and coordination.
45.
46. 3. Alkaptonuria
Alkaptonuria is an inborn metabolic disease transmitted as an autosomal
recessive gene, the HGD gene
which causes the lack of the enzyme homogentisate oxidase, which is needed
in the metabolism of tyrosine and phenylalanine.
This disorder occurs in about 1 of 250,000 births.
A predominant clinical manifestation of alkaptonuria is that the patient’s
urine turns brownish-black when it mixes with air.
This phenomenon is due to an accumulation in the urine of homogentisic acid
(HGA), which oxidizes to produce this dark pigment.
47.
48. CONT..
Alkaptonuric patients have no immediate problems; however, late in the
disease, the high level of HGA gradually accumulates in connective tissue,
causing ochronosis (pigmentation of these tissues), an arthritis-like
degeneration from the buildup of homogentisic acid in the cartilage, dark
spots on the sclera (white of the eye), and deposition of pigment in the
cartilage of the ears, nose, and tendons of the extremities.
Urinalysis is done to test for alkaptonuria.
When ferric chloride is added to the urine, it will turn the urine black in
patients with alkaptonuria.
Treatment for alkaptonuria is high-dose vitamin C, which has been shown to
decrease the buildup of brown pigment in the cartilage and may slow the
development of arthritis.
49. 4. MAPLE SYRUP URINE DISEASE
Maple syrup urine disease (MSUD) results from an absence or greatly reduced
activity of the enzyme branched-chain alpha-ketoacid decarboxylase
blocking the normal metabolism of the three essential branched-chain amino
acids leucine, isoleucine, and valine.
MSUD is an autosomal recessive genetic inherited disorder.
Newborn screening for MSUD has been part of several state screening
programs since the mid-1970s with a reported prevalence of 1 in 150,000
births in the general population.
The most striking feature of this hereditary disease is the characteristic
maple syrup or burnt sugar odor of the urine, breath, and skin. The result of
this enzyme defect is an accumulation of the branched-chain amino acids and
their corresponding ketoacids in the blood, urine, and cerebrospinal fluid
(CSF).
50.
51. 5. ISOVALERIC ACIDEMIA
Isovaleric acidemia is an autosomal recessive metabolic disorder
from a deficiency of the enzyme isovaleryl-CoA dehydrogenase
preventing normal metabolism of the branched-chain amino acid leucine.
The prevalence of Isovaleric acidemia is approximately 1 in 250,000 births in
the United States, caused by mutations in the isovalerylCoA dehydrogenase
(IVD) gene.
52. CONT..
A characteristic feature of isovaleric acidemia is a distinctive odor of sweaty
feet caused by the buildup of isovaleric acid.
Health problems related to isovaleric acidemia range from very mild to life-
threatening, but when severe, it can damage the brain and nervous system.
Clinical manifestations of this disorder become apparent a few days after
birth and include failure to thrive, vomiting, and lethargy that can progress to
seizures, coma, and possibly death.
Some people with gene mutations that cause isovaleric acidemia are
asymptomatic and never experience any signs and symptoms of the condition.
53.
54. 6. HOMOCYSTINURIA
Homocystinuria is yet another inherited autosomal recessive disorder of amino
acid metablolism.
it is the lack of the enzyme cystathionine-beta synthetase, necessary for the
metabolism of the amino acid methionine
results in elevated plasma and urine levels of methionine and of the precursor
homocysteine.
The incidence of this disease is about 1 in 200,000 births.
Infants seem to be healthy, and early symptoms, if any, are indistinct.
Associated clinical findings in late childhood include osteoporosis, dislocated
lenses in the eye resulting from the lack of cysteine synthesis essential for
collagen formation, and, frequently, mental retardation.
This defect leads to a multisystemic disorder of the connective tissue, muscles,
CNS, thinning and weakening of bones, and thrombosis resulting from the toxicity
of homocysteine to the vascular endothelium if it goes untreated.
58. 7. CYSTINURIA
Cystinuria is an inherited autosomal recessive defect
caused by a defect in the amino acid transport system rather than a
metabolic enzyme deficiency.
Cystinuria is characterized by the inadequate reabsorption of cystine during
the filtering process in the kidneys
resulting in an excessive concentration of this amino acid.
Cystine precipitates out of the urine and forms stones in the kidneys, ureters,
or bladder. The kidney stones often recur throughout a patient’s lifetime and
are directly or indirectly responsible for all of the signs and symptoms of the
disease, including hematuria, pain in the side due to kidney pain, and urinary
tract infections.
59. Sr. No Disorder
name
Amino acid Enzyme absent Disease ratio
1 Phenylketonuria
(PKU)
phenylalanine phenylalanine hydroxylase
(PAH)
1 in 15,000 births
2 Tyrosinemia
( has 3 types)
Type I tyrosinemia phenylalanine fumarylacetoacetate
hydrolase
1 in 100,000 births.
Type II tyrosinemia tyrosine Tyrosine aminotransferase 1 in 250,000 births.
Type III tyrosinemia p-OHphenylpyruvate 4-hydroxyphenylpyruvate
dioxygenase
Rare disorder
3 Alkaptonuria homogentisic acid homogentisate oxidase 1 of 250,000 births
4 Maple syrup urine
disease (MSUD)
Not mentioned in book alpha-ketoacid
decarboxylase
1 in 150,000 births
5 Isovaleric Acidemia Not mentioned in book isovaleryl-CoA
dehydrogenase
1 in 250,000 births
6 Homocystinuria Homocysteine (Hcy) cystathionine-beta
synthetase
1 in 200,000 births