The 3-Hydroxypropionate bicycle, also known as the 3-Hydroxypropionate pathway, is a process that allows some bacteria to generate
3-Hydroxypropionate utilizing
carbon dioxide
Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
. In this pathway CO
2 is fixed (i.e. incorporated) by the action of two
enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...
s,
acetyl-CoA carboxylase
Acetyl-CoA carboxylase (ACC) is a biotin-dependent enzyme () that catalyzes the irreversible carboxylation of acetyl-CoA to produce malonyl-CoA through its two catalytic activities, biotin carboxylase (BC) and carboxyltransferase (CT). ACC is ...
and
propionyl-CoA carboxylase
Propionyl-CoA carboxylase (, PCC) catalyses the carboxylation reaction of propionyl-CoA in the mitochondrial matrix. PCC has been classified both as a ligase and a lyase. The enzyme is biotin-dependent. The product of the reaction is (S)-methylmal ...
. These enzymes generate
malonyl-CoA
Malonyl-CoA is a coenzyme A derivative of malonic acid.
Functions
It plays a key role in chain elongation in fatty acid biosynthesis and polyketide biosynthesis.
Fatty acid biosynthesis
Malonyl-CoA provides 2-carbon units to fatty acids and commi ...
and
(''S'')-methylmalonyl-CoA, respectively. Malonyl-CoA, in a series of reactions is further split into
acetyl-CoA
Acetyl-CoA (acetyl coenzyme A) is a molecule that participates in many biochemical reactions in protein, carbohydrate and lipid metabolism. Its main function is to deliver the acetyl group to the citric acid cycle (Krebs cycle) to be oxidized for ...
and
glyoxylate
Glyoxylic acid or oxoacetic acid is an organic compound. Together with acetic acid, glycolic acid, and oxalic acid, glyoxylic acid is one of the C2 carboxylic acids. It is a colourless solid that occurs naturally and is useful industrially.
Str ...
.
Glyoxylate
Glyoxylic acid or oxoacetic acid is an organic compound. Together with acetic acid, glycolic acid, and oxalic acid, glyoxylic acid is one of the C2 carboxylic acids. It is a colourless solid that occurs naturally and is useful industrially.
Str ...
is incorporated into beta-methylmalyl-coA which is then split, again through a series of reactions to release pyruvate as well as acetate, which is used to replenish the cycle. This pathway has been demonstrated in ''
Chloroflexus
Chloroflexales is an order of bacteria in the class Chloroflexia.
Taxonomy
The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) and National Center for Biotechnology Information (NCBI).
* ...
'', a nonsulfur photosynthetic bacterium, however other studies suggest that 3-hydroxypropionate bicycle is utilized by several
chemotrophic
A Chemotroph is an organism that obtains energy by the oxidation of electron donors in their environments. These molecules can be organic (chemoorganotrophs) or inorganic ( chemolithotrophs). The chemotroph designation is in contrast to phototro ...
archaea
Archaea ( ; singular archaeon ) is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaebac ...
.
See also
*
Carbon fixation
Biological carbon fixation or сarbon assimilation is the process by which inorganic carbon (particularly in the form of carbon dioxide) is converted to organic compounds by living organisms. The compounds are then used to store energy and as ...
References
External links
Pathways
Metabolic pathways
{{biochem-stub