Biotinidase
Encyclopedia
Biotinidase also known as BTD is an enzyme
that in humans is encoded by the BTD gene
.
, sometimes called vitamin H. Biotinidase extracts biotin from food because the body needs biotin in its free, unattached form. This enzyme also recycles biotin from enzymes in the body that use it as a helper component in order to function. These enzymes, known as carboxylases, are important in the processing of fat
s, carbohydrate
s, and protein
s. Biotin is attached to these carboxylase enzymes through an amino acid
(the building material of proteins) called lysine
, forming a complex called biocytin
. Biotinidase removes biotin from biocytin and makes it available to be reused by other enzymes.
, sometimes called vitamin H, is an important water-soluble vitamin that aids in the metabolism
of fat
s, carbohydrate
s and protein
s. The human body cannot produce biotin, but it can obtain it from the diet, internal recycling and at some extent from intestinal bacteria. Biotin deficiency
can result in behavioral disorders, lack of coordination, learning disabilities and seizure.
Unlike most vitamins, which are noncovalently bound to enzymes, biotin is chemically linked (covalently bound), and therefore cannot be easily removed from the enzyme denaturation
. Without biotinidase activity, the vitamin biotin cannot be separated from foods and therefore cannot be used by the body. Biotinidase deficiency
is an inherited disorder caused by mutation
s in the BTD gene. When biotinidase activity is deficient, biotin can be neither recycled within the body nor removed from ingested food. Nor can biotin be recycled from enzymes to which it is bound. Deficient biotinidase activity causes specific metabolic enzymes, called carboxylases, to be nonfunctional, inhibiting the proper processing of proteins, fats, and carbohydrates. Individuals lacking biotinidase activity can still have normal carboxylases if they ingest small amounts of biotin.
Approximately 1 in 60,000 newborns are affected by profound (less than 10 percent of normal enzyme activity) or partial (10-30 percent of normal enzyme activity) biotinidase deficiency.
at position 25, from base pair
15,618,326 to base pair 15,662,328. Mutation
s in the BTD gene
cause biotinidase deficiency.
Approximately 100 mutations in the BTD gene that lead to biotinidase deficiency have been discovered. These mutations either prevent the enzyme from being made or cause the enzyme that is produced to be nonfunctional.
This condition is inherited in an autosomal recessive pattern, which means two copies of the gene in each cell must be altered for a person to be affected by the disorder. Most often, the parents of a child with an autosomal recessive disorder are not affected but are carriers of one copy of the altered gene.
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
that in humans is encoded by the BTD gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
.
Function
This enzyme allows the body to use and to recycle the B vitamin biotinBiotin
Biotin, also known as Vitamin H or Coenzyme R, is a water-soluble B-complex vitamin discovered by Bateman in 1916. It is composed of a ureido ring fused with a tetrahydrothiophene ring. A valeric acid substituent is attached to one of the carbon atoms of the tetrahydrothiophene ring...
, sometimes called vitamin H. Biotinidase extracts biotin from food because the body needs biotin in its free, unattached form. This enzyme also recycles biotin from enzymes in the body that use it as a helper component in order to function. These enzymes, known as carboxylases, are important in the processing of fat
Fat
Fats consist of a wide group of compounds that are generally soluble in organic solvents and generally insoluble in water. Chemically, fats are triglycerides, triesters of glycerol and any of several fatty acids. Fats may be either solid or liquid at room temperature, depending on their structure...
s, carbohydrate
Carbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...
s, and protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s. Biotin is attached to these carboxylase enzymes through an amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
(the building material of proteins) called lysine
Lysine
Lysine is an α-amino acid with the chemical formula HO2CCH4NH2. It is an essential amino acid, which means that the human body cannot synthesize it. Its codons are AAA and AAG....
, forming a complex called biocytin
Biocytin
Biocytin is a chemical compound that is an amide formed from the vitamin biotin and the amino acid L-lysine. As an intermediate in the metabolism of biotin, biocytin occurs naturally in blood serum and urine....
. Biotinidase removes biotin from biocytin and makes it available to be reused by other enzymes.
Clinical significance
BiotinBiotin
Biotin, also known as Vitamin H or Coenzyme R, is a water-soluble B-complex vitamin discovered by Bateman in 1916. It is composed of a ureido ring fused with a tetrahydrothiophene ring. A valeric acid substituent is attached to one of the carbon atoms of the tetrahydrothiophene ring...
, sometimes called vitamin H, is an important water-soluble vitamin that aids in the metabolism
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...
of fat
Fat
Fats consist of a wide group of compounds that are generally soluble in organic solvents and generally insoluble in water. Chemically, fats are triglycerides, triesters of glycerol and any of several fatty acids. Fats may be either solid or liquid at room temperature, depending on their structure...
s, carbohydrate
Carbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...
s and protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s. The human body cannot produce biotin, but it can obtain it from the diet, internal recycling and at some extent from intestinal bacteria. Biotin deficiency
Biotin deficiency
Biotin deficiency is a rare nutritional disorder which can become serious, even fatal, if allowed to progress untreated. It can occur in people of any age, ancestry, or gender...
can result in behavioral disorders, lack of coordination, learning disabilities and seizure.
Unlike most vitamins, which are noncovalently bound to enzymes, biotin is chemically linked (covalently bound), and therefore cannot be easily removed from the enzyme denaturation
Denaturation (biochemistry)
Denaturation is a process in which proteins or nucleic acids lose their tertiary structure and secondary structure by application of some external stress or compound, such as a strong acid or base, a concentrated inorganic salt, an organic solvent , or heat...
. Without biotinidase activity, the vitamin biotin cannot be separated from foods and therefore cannot be used by the body. Biotinidase deficiency
Biotinidase deficiency
Biotinidase deficiency is an autosomal recessive metabolic disorder in which biotin is not released from proteins in the diet during digestion or from normal protein turnover in the cell. This situation results in biotin deficiency....
is an inherited disorder caused by mutation
Mutation
In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...
s in the BTD gene. When biotinidase activity is deficient, biotin can be neither recycled within the body nor removed from ingested food. Nor can biotin be recycled from enzymes to which it is bound. Deficient biotinidase activity causes specific metabolic enzymes, called carboxylases, to be nonfunctional, inhibiting the proper processing of proteins, fats, and carbohydrates. Individuals lacking biotinidase activity can still have normal carboxylases if they ingest small amounts of biotin.
Approximately 1 in 60,000 newborns are affected by profound (less than 10 percent of normal enzyme activity) or partial (10-30 percent of normal enzyme activity) biotinidase deficiency.
Genetics
The BTD gene is located on the short (p) arm of chromosome 3Chromosome 3 (human)
Chromosome 3 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 3 spans almost 200 million base pairs and represents about 6.5 percent of the total DNA in cells....
at position 25, from base pair
Base pair
In molecular biology and genetics, the linking between two nitrogenous bases on opposite complementary DNA or certain types of RNA strands that are connected via hydrogen bonds is called a base pair...
15,618,326 to base pair 15,662,328. Mutation
Mutation
In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...
s in the BTD gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
cause biotinidase deficiency.
Approximately 100 mutations in the BTD gene that lead to biotinidase deficiency have been discovered. These mutations either prevent the enzyme from being made or cause the enzyme that is produced to be nonfunctional.
This condition is inherited in an autosomal recessive pattern, which means two copies of the gene in each cell must be altered for a person to be affected by the disorder. Most often, the parents of a child with an autosomal recessive disorder are not affected but are carriers of one copy of the altered gene.