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Holocarboxylase synthetase (biotin—(propionyl-Coenzyme A-carboxylase (ATP-hydrolysing)) ligase)), also known as protein—biotin ligase, is a family of enzymes ({{{EnzExplorer, 6.3.4.10). This enzyme is important for the effective use of biotin, a B vitamin found in foods such as
liver The liver is a major organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it ...
, egg yolks, and
milk Milk is a white liquid food produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals (including breastfed human infants) before they are able to digest solid food. Immune factors and immune-modula ...
. In many of the body's tissues, holocarboxylase synthetase activates other specific enzymes (called biotin-dependent carboxylases) by attaching biotin to them. These carboxylases are involved in many critical cellular functions, including the production and breakdown of proteins, fats, and carbohydrates. The catalyzed reaction: :ATP + biotin + apo- propionyl-CoA:carbon-dioxide ligase (ADP-forming) \rightleftharpoons AMP + diphosphate + propionyl-CoA:carbon-dioxide ligase (ADP-forming) The 3 substrates of this enzyme are ATP, biotin, and apo-[propionyl-CoA:carbon-dioxide_ligase_(ADP-forming),_whereas_its_3_
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, diphosphate, and propionyl-CoA:carbon-dioxide ligase (ADP-forming). Holocarboxylase synthetase may also play a role in regulating the activity of genes. In the nucleus, the enzyme likely attaches biotin molecules to histones, which are structural proteins that bind to DNA and give chromosomes their shape. Changing the shape of histones may help determine whether certain genes are turned on or off; however, it is not known how adding biotin affects gene regulation. The HLCS gene is located on the long (q) arm of
chromosome 21 Chromosome 21 is one of the 23 pairs of chromosomes in humans. Chromosome 21 is both the smallest human autosome and chromosome, with 48 million base pairs (the building material of DNA) representing about 1.5 percent of the total DNA in cells. M ...
at position 22.1, from base pair 37,045,059 to base pair 37,284,372.


Related conditions

Holocarboxylase synthetase deficiency: About 30
mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA replication, DNA or viral repl ...
s in the HLCS gene have been identified in people with holocarboxylase synthetase deficiency. Most of these mutations substitute one
amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha a ...
(a building block of proteins) for another amino acid in the holocarboxylase synthetase enzyme. Many of the known mutations occur in a region of the enzyme that binds to biotin. These mutations reduce the enzyme's ability to attach biotin to carboxylases and
histone In biology, histones are highly basic proteins abundant in lysine and arginine residues that are found in eukaryotic cell nuclei. They act as spools around which DNA winds to create structural units called nucleosomes. Nucleosomes in turn a ...
s. Without biotin, carboxylases remain inactive and are unable to process
protein 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, res ...
s,
fat In nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such compounds, most commonly those that occur in living beings or in food. The term often refers specifically to triglycerides (triple est ...
s, and
carbohydrate In organic chemistry, a carbohydrate () is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula (where ''m'' may or m ...
s. A lack of holocarboxylase synthetase activity may also alter the regulation of certain genes that are important for normal development. Researchers believe that these disruptions in important cellular functions lead to breathing problems, skin rashes, and the other characteristic signs and symptoms of holocarboxylase synthetase deficiency.


See also

*
Biotinylation In biochemistry, biotinylation is the process of covalently attaching biotin to a protein, nucleic acid or other molecule. Biotinylation is rapid, specific and is unlikely to disturb the natural function of the molecule due to the small size of bi ...


References

* {{cite journal , vauthors = Siegel L, Foote JL, Coon MJ , title = The enzymatic synthesis of propionyl coenzyme A holocarboxylase from d-biotinyl 5'-adenylate and the apocarboxylase , journal = The Journal of Biological Chemistry , volume = 240 , pages = 1025–31 , date = March 1965 , issue = 3 , doi = 10.1016/S0021-9258(18)97532-0 , pmid = 14284697 , doi-access = free


External links

* {{MeshName, holocarboxylase+synthetases {{Ligases CO CS and CN {{Enzymes {{Portal bar, Biology, border=no EC 6.3.4 Enzymes of unknown structure {{6.3-enzyme-stub