In organic chemistry, a tetrose is a monosaccharide with 4 carbon atoms. They have either an aldehyde functional group in position 1 (aldotetroses) or a ketone group in position 2 (ketotetroses).
Pyridoxal phosphate (PLP, pyridoxal 5'-phosphate, P5P), the active form of vitamin B6, is a coenzyme in a variety of enzymatic reactions. The International Union of Biochemistry and Molecular Biology has catalogued more than 140 PLP-dependent activities, corresponding to ~4% of all classified activities. The versatility of PLP arises from its ability to covalently bind the substrate, and then to act as an electrophilic catalyst, thereby stabilizing different types of carbanionic reaction intermediates.
The Calvin cycle, light-independent reactions, bio synthetic phase, dark reactions, or photosynthetic carbon reduction (PCR) cycle of photosynthesis is a series of chemical reactions that convert carbon dioxide and hydrogen-carrier compounds into glucose. The Calvin cycle is present in all photosynthetic eukaryotes and also many photosynthetic bacteria. In plants, these reactions occur in the stroma, the fluid-filled region of a chloroplast outside the thylakoid membranes. These reactions take the products of light-dependent reactions and perform further chemical processes on them. The Calvin cycle uses the chemical energy of ATP and reducing power of NADPH from the light dependent reactions to produce sugars for the plant to use. These substrates are used in a series of reduction-oxidation (redox) reactions to produce sugars in a step-wise process; there is no direct reaction that converts several molecules of CO2 to a sugar. There are three phases to the light-independent reactions, collectively called the Calvin cycle: carboxylation, reduction reactions, and ribulose 1,5-bisphosphate (RuBP) regeneration.
Glyceraldehyde 3-phosphate, also known as triose phosphate or 3-phosphoglyceraldehyde and abbreviated as G3P, GA3P, GADP, GAP, TP, GALP or PGAL, is a metabolite that occurs as an intermediate in several central pathways of all organisms. With the chemical formula H(O)CCH(OH)CH2OPO32-, this anion is a monophosphate ester of glyceraldehyde.
Aldolase A, also known as fructose-bisphosphate aldolase, is an enzyme that in humans is encoded by the ALDOA gene on chromosome 16.
Dihydroxyacetone phosphate (DHAP, also glycerone phosphate in older texts) is the anion with the formula HOCH2C(O)CH2OPO32-. This anion is involved in many metabolic pathways, including the Calvin cycle in plants and glycolysis. It is the phosphate ester of dihydroxyacetone.
Triose-phosphate isomerase is an enzyme that catalyzes the reversible interconversion of the triose phosphate isomers dihydroxyacetone phosphate and D-glyceraldehyde 3-phosphate.
Transketolase is an enzyme that, in humans, is encoded by the TKT gene. It participates in both the pentose phosphate pathway in all organisms and the Calvin cycle of photosynthesis. Transketolase catalyzes two important reactions, which operate in opposite directions in these two pathways. In the first reaction of the non-oxidative pentose phosphate pathway, the cofactor thiamine diphosphate accepts a 2-carbon fragment from a 5-carbon ketose (D-xylulose-5-P), then transfers this fragment to a 5-carbon aldose (D-ribose-5-P) to form a 7-carbon ketose (sedoheptulose-7-P). The abstraction of two carbons from D-xylulose-5-P yields the 3-carbon aldose glyceraldehyde-3-P. In the Calvin cycle, transketolase catalyzes the reverse reaction, the conversion of sedoheptulose-7-P and glyceraldehyde-3-P to pentoses, the aldose D-ribose-5-P and the ketose D-xylulose-5-P.
Aldolase B also known as fructose-bisphosphate aldolase B or liver-type aldolase is one of three isoenzymes of the class I fructose 1,6-bisphosphate aldolase enzyme, and plays a key role in both glycolysis and gluconeogenesis. The generic fructose 1,6-bisphosphate aldolase enzyme catalyzes the reversible cleavage of fructose 1,6-bisphosphate (FBP) into glyceraldehyde 3-phosphate and dihydroxyacetone phosphate (DHAP) as well as the reversible cleavage of fructose 1-phosphate (F1P) into glyceraldehyde and dihydroxyacetone phosphate. In mammals, aldolase B is preferentially expressed in the liver, while aldolase A is expressed in muscle and erythrocytes and aldolase C is expressed in the brain. Slight differences in isozyme structure result in different activities for the two substrate molecules: FBP and fructose 1-phosphate. Aldolase B exhibits no preference and thus catalyzes both reactions, while aldolases A and C prefer FBP.
Erythrose 4-phosphate is a phosphate of the simple sugar erythrose. It is an intermediate in the pentose phosphate pathway and the Calvin cycle.
Fructose-bisphosphate aldolase, often just aldolase, is an enzyme catalyzing a reversible reaction that splits the aldol, fructose 1,6-bisphosphate, into the triose phosphates dihydroxyacetone phosphate (DHAP) and glyceraldehyde 3-phosphate (G3P). Aldolase can also produce DHAP from other (3S,4R)-ketose 1-phosphates such as fructose 1-phosphate and sedoheptulose 1,7-bisphosphate. Gluconeogenesis and the Calvin cycle, which are anabolic pathways, use the reverse reaction. Glycolysis, a catabolic pathway, uses the forward reaction. Aldolase is divided into two classes by mechanism.
Ribose-5-phosphate isomerase (Rpi) encoded by the RPIA gene is an enzyme that catalyzes the conversion between ribose-5-phosphate (R5P) and ribulose-5-phosphate (Ru5P). It is a member of a larger class of isomerases which catalyze the interconversion of chemical isomers. It plays a vital role in biochemical metabolism in both the pentose phosphate pathway and the Calvin cycle. The systematic name of this enzyme class is D-ribose-5-phosphate aldose-ketose-isomerase.
Cystathionine beta-lyase, also commonly referred to as CBL or β-cystathionase, is an enzyme that primarily catalyzes the following α,β-elimination reaction
The enzyme 2-dehydro-3-deoxy-phosphogluconate aldolase, commonly known as KDPG aldolase, catalyzes the chemical reaction
The enzyme diaminopimelate decarboxylase (EC 4.1.1.20) catalyzes the cleavage of carbon-carbon bonds in meso-2,6-diaminoheptanedioate (diaminopimelate) to produce CO2 and L-lysine, the essential amino acid. It employs the cofactor pyridoxal phosphate, also known as PLP, which participates in numerous enzymatic transamination, decarboxylation and deamination reactions.
The enzyme phosphoketolase(EC 4.1.2.9) catalyzes the chemical reactions
Aldolase C, fructose-bisphosphate, is an enzyme that, in humans, is encoded by the ALDOC gene on chromosome 17. This gene encodes a member of the class I fructose-bisphosphate aldolase gene family. Expressed specifically in the hippocampus and Purkinje cells of the brain, the encoded protein is a glycolytic enzyme that catalyzes the reversible aldol cleavage of fructose 1,6-bisphosphate and fructose-1-phosphate to dihydroxyacetone phosphate and either glyceraldehyde 3-phosphate or glyceraldehyde, respectively.[provided by RefSeq, Jul 2008]
Transaldolase deficiency is a disease characterised by abnormally low levels of the transaldolase enzyme. It is a metabolic enzyme involved in the pentose phosphate pathway. It is caused by mutation in the transaldolase gene (TALDO1). It was first described by Verhoeven et al. in 2001.
Transaldolase 1 is a protein that in humans is encoded by the TALDO1 gene.
Sulfoglycolysis is a catabolic process in primary metabolism in which sulfoquinovose (6-deoxy-6-sulfonato-glucose) is metabolized to produce energy and carbon-building blocks. Sulfoglycolysis pathways occur in a wide variety of organisms, and enable key steps in the degradation of sulfoquinovosyl diacylglycerol (SQDG), a sulfolipid found in plants and cyanobacteria into sulfite and sulfate. Sulfoglycolysis converts sulfoquinovose (C6H12O8S−) into various smaller metabolizable carbon fragments such as pyruvate and dihydroxyacetone phosphate that enter central metabolism. The free energy is used to form the high-energy molecules ATP (adenosine triphosphate) and NADH (reduced nicotinamide adenine dinucleotide). Unlike glycolysis, which allows metabolism of all carbons in glucose, sulfoglycolysis pathways convert only a fraction of the carbon content of sulfoquinovose into smaller metabolizable fragments; the remainder is excreted as C3-sulfonates 2,3-dihydroxypropanesulfonate (DHPS) or sulfolactate (SL); or C2-sulfonates isethionate or sulfoacetate.
