Scichimic acid pathway: secondary metabolic pathway that has scichimic acid as its precursor, a molecule that contains within itself those structural and chemical characteristics that can be found in the secondary metabolites that originate from it.
The molecule of scichimic acid is made up of: a 6-membered ring, 1 carboxylic group and 3 hydroxyl groups. This same molecular architecture can be found in the secondary metabolites that originate from it, and which are called, in fact, derivatives of the acid. scichimic. Scichimic acid originates from the union of two intermediates of two different primary metabolic pathways:
erythrosium-4-phosphate (3C): intermediate of the dark phase of photosynthesis, anabolic metabolic process;
phosphoenolpyruvic acid (3C): intermediate of glycolysis, catabolic metabolic process;
Therefore, erythrosium-4-phosphate + phosphoenolpyruvic acid = scichimic acid: first precursor of secondary metabolic pathways.
The cell synthesizes the scichimic acid when the needs are such as to allow it, or when the quantities of the two primary intermediates are so many and such that they can accumulate; this happens when there is a sufficient quantity of ATP in the cell and this slows down the reactions of primary catabolism and anabolism.
Path of malonic and mevalonic acid: both precursors derive from a molecule of Acetyl CoA, therefore both underlie a single path: the acetate pathway. Acetyl CoA is a connection molecule between glycolysis and Krebs cycle and we can therefore define it as an intermediate of the primary metabolism of the cell.
Acetate group (group with two carbon atoms) + CoA (coenzyme A) = Acetyl CoA: molecule belonging to the primary metabolism, which is used as a biological building block in the construction of secondary metabolites.
The acetate pathway is then distinguished by the malonic acid pathway and the mevalonic acid pathway. Coenzyme A acts as a transport of the two carbonaceous units from the cytoplasm to the mitochondrion of the cell, where the Krebs cycle takes place. of carbon are instead transported elsewhere in case of energy surplus and can go to constitute the most varied secondary metabolites; these have an even number of carbon atoms as a common feature, including malonic acid (C4) and mevalonic (C6 ).
The metabolic pathways of scichimic acid and acetate therefore possess a precise molecular architecture, which allows us to easily identify their secondary derivatives. For the alkaloids, which have diversified architectures, the identification of the precursor is not so easy; in other words, it is not so easy to classify the single categories of alkaloids, tracing each one to a single precursor. Alkaloids, in fact, have more than one precursor, since they derive from amino acids (primary nitrogen compounds, which the cell uses to produce secondary nitrogen molecules). The secondary nitrogen metabolites are mainly alkaloids, but there are also other molecules with a lower health profile than their own, such as cyanogenic glycosides (contained in bitter almonds) and β-cyanos (pigments) Amino acids are nitrogenous compounds diversified from each other and this diversity reflects the diversification of their direct derivatives, which are the alkaloids.
The only chemical element that unites the different categories of alkaloids is a nitrogen atom enclosed in a heterocyclic ring, or at least a nitrogen atom with a free electron doublet that gives them basic properties; the same basic reactivity that allows us to extract the individual alkaloids by displacement.
We can sum it up by saying that the carbohydrate pathway is the metabolic pathway underlying the synthesis of all secondary metabolites, therefore it includes all the metabolic pathways previously seen:
- acetate is the product of the complete demolition of the glucose molecule;
- amino acids derive from metabolic processes of carbohydrate degradation;
- scichimic acid is a precursor of secondary metabolites, but also of aromatic amino acids (phenylalanine, tryptophan and tyrosine);
-the glycoside is a secondary metabolite composed of a sugar plus a non-sugar unit, called aglycone, which presumably derives from one of the metabolic pathways summarized.
All the biogenetic building blocks from which secondary metabolites originate derive either from the catabolism of carbohydrates or from their anabolism. These sugars are the same sugar units that once bound to the aglycone constitute the glycosides.
The metabolic pathway of acetate is divided into a dense biogenetic tree, containing all the names of the secondary metabolites to which it gives rise. different, depending on the needs of the cell itself:
- Krebs cycle with final production of ATP (primary metabolism);
- β-oxidation and synthesis of fatty acids (primary metabolism);
- Synthesis of malonate or malonic acid (4C), deriving from the union of two acetate molecules, and of mevalonate or mevalonic acid (6C) deriving from the union of three acetate molecules. The cell uses these two molecules with an even number of carbon atoms to build different molecular categories, consisting of linear chains of hydrocarbon units, such as: fatty acids - used in turn to produce glycerides and waxes - terpenoids, anthraquinones and steroids.
Other articles on "Biogenesis and characteristics of the active ingredients"
- Primary metabolism and secondary metabolism of a plant
- Pharmacognosy
- Metabolic pathway of scichimic acid
