Argininemia is an

autosomal An autosome is any chromosome that is not a sex chromosome. The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosome, allosomal (sex chromosome) pairs, which may have different structures. The DNA in au ...

recessive In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and t ...

urea cycle disorder Urea, also known as carbamide, is an organic compound with chemical formula . This amide has two amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest amide of carbamic acid. Urea serves an important r ...

where a deficiency of the enzyme

arginase Arginase (, ''arginine amidinase'', ''canavanase'', ''L-arginase'', ''arginine transamidinase'') is a manganese-containing enzyme. The reaction catalyzed by this enzyme is: : arginine + H2O → ornithine + urea It is the final enzyme of the ure ...

causes a buildup of

arginine Arginine is the amino acid with the formula (H2N)(HN)CN(H)(CH2)3CH(NH2)CO2H. The molecule features a guanidino group appended to a standard amino acid framework. At physiological pH, the carboxylic acid is deprotonated (−CO2−) and both the am ...

and

ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous was ...

in the

blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the c ...

. Ammonia, which is formed when

proteins Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

are broken down in the body, is toxic if levels become too high; the

nervous system In biology, the nervous system is the highly complex part of an animal that coordinates its actions and sensory information by transmitting signals to and from different parts of its body. The nervous system detects environmental changes th ...

is especially sensitive to the effects of excess ammonia.update 2014

Signs and symptoms

The presentation of argininemia, in those that are affected, is consistent with the following:

Genetics

Mutations in the ''

ARG1 The human ARG1 gene encodes the protein arginase. Function Arginase catalyzes the hydrolysis of arginine to ornithine and urea. At least two isoforms of mammalian arginase exist (types I and II) which differ in their tissue distribution, sub ...

'' gene cause argininemia, which belongs to a class of genetic diseases called

urea cycle The urea cycle (also known as the ornithine cycle) is a cycle of biochemical reactions that produces urea (NH2)2CO from ammonia (NH3). Animals that use this cycle, mainly amphibians and mammals, are called ureotelic. The urea cycle converts highl ...

disorders.update 2015 The urea cycle is a sequence of reactions that occurs in

liver The liver is a major Organ (anatomy), organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of proteins and biochemicals necessary for ...

cells (hepatocytes). This cycle processes excess

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

, generated when protein is used by the body, making

urea Urea, also known as carbamide, is an organic compound with chemical formula . This amide has two amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest amide of carbamic acid. Urea serves an important r ...

that is excreted via the kidneys. The ''ARG1'' gene provides instructions for making an enzyme called

, this enzyme controls the last steps of the urea cycle, which produces urea by extracting nitrogen from arginine. In people with arginase deficiency, arginase is missing, and arginine is not broken down properly. consequently, urea cannot be produced and excess nitrogen accumulates in the blood in the form of

. Ammonia and arginine are thought to cause neurological problems and other symptoms of arginase deficiency. This condition is an autosomal recessive disorder, which means the defective

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...

is located on an

autosome An autosome is any chromosome that is not a sex chromosome. The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosome, allosomal (sex chromosome) pairs, which may have different structures. The DNA in au ...

, and two copies of the defective gene are required to inherit the disorder. Both parents of an individual with an autosomal recessive disorder are carriers of one copy of the gene, but usually do not have the disorder.

Diagnosis

The diagnosis for argininemia can usually be done using fetal blood sample. One can look for the following indicators as to the presence of the condition: * Plasma ammonia concentration. * Urinary

orotic acid Orotic acid is a pyrimidinedione and a carboxylic acid. Historically, it was believed to be part of the vitamin B complex and was called vitamin B13, but it is now known that it is not a vitamin. The compound is synthesized in the body via a mi ...

concentration *

Red blood cell Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek ''erythros'' for "red" and ''kytos'' for "holl ...

arginase enzyme activity (measurement)

Treatment

The treatment for infants (individuals) with argininemia is the following, including medications:

References

External links