Cyclodipeptide synthases (CDPSs) are a newly defined family of peptide-bond forming enzymes that are responsible for the ribosome-independent biosynthesis of various cyclodipeptides, which are the precursors of many natural products with important biological activities. [1] [2] As a substrate for this synthesis, CDPSs use two amino acids activated as aminoacyl-tRNAs (aa-tRNAs), therefore diverting them from the ribosomal machinery. [3] [4] [5] The first member of this family was identified in 2002 during the characterization of the albonoursin biosynthetic pathway in Streptomyces noursei. [6] CDPSs are present in bacteria, fungi, and animal cells. [7]
From 2002, when the first description of a CDPSs was done, until now, the number of reported CDPSs in databases has experienced a significant growth (800 in June 2017). It is probable that these cyclopeptides are implicated in numerous biosynthetic pathways. However, their products’ diversity has not been very explored. The activity of 32 new CPDS has been described. [8] This fact raises the number of experimentally characterized CDPS up to 100 (approximately). Moreover, this research has identified several consensus sequences associated to the formation of a specific cyclodipeptide, enhancing the predictive model of specificity of CDPS. This improved prediction method facilitates the deciphering of independent ways of CDPS. [9]
CDPSs don’t have a specific structure, given each one has its own specific function, but they still have common architectures, such as a Rossmann-fold domain. CDPSs are monomers that have been found to display a strong structural similarity to the catalytic domains of class Ic aminoacyl tRNA synthetases: both these families, CDPSs and class Ic aaRSs, have a Rossmann-fold domain and their structures can be superimposed showing many structural analogies.
CDPSs characteristically feature a deep surface-accessible pocket bordered by the catalytic residues, which is where the catalysis of amide bond formation takes place. This structure is positioned similarly to the aminoacyl binding pocket in aaRSs, which leads to thinking that CDPSs evolved from class Ic aaRSs.
CDPSs and aaRSs present substantial differences though, such as the absence of ATP-binding motifs in CDPSs, given that these use, unlike aaRSs, amino acids that have already been activated. [3]
It was firstly thought that nonribosomal peptide synthetases (NRPSs) were the responsible ones of CDPs construction, either through specific biosynthetic pathways or with the premature liberation of dipeptidyl intermediates meanwhile the elongation process was done. [10] On account of AlbC discovery, an enzyme with the ability to specifically create CDP using loaded ARNt as substrates, it was disclosed that there was a second route for the cyclodipeptide production. [11]
CDPSs' catalytic cycle begins with the binding of the first aa-tRNA, with its aminoacyl transferred onto a conserved serine residue to form an aminoacyl-enzyme intermediate. The second aa-tRNA interacts with this intermediate so that its aminoacyl is transferred to the aminoacyl-enzyme to form a dipeptidyl-enzyme intermediate. Finally, the dipeptidyl goes through an intramolecular cyclization leading to the final cyclodipeptide. [3]
CDPSs can be divided into two distinct subfamilies named NYH and XYP, distinguished depending on the conserved residues within their respective active sites, which let experts predict their aminoacyl-tRNA substrates. [7] [3] Both subfamilies mainly differ in the first half of their Rossmann fold, this two structures correspond to two different structural solutions to facilitate the reactivity of the catalytic serine residue. [12] Some NYH’s crystal structures have been identified. These CDPSs’ structure contain a Rossmann fold domain.
NYH form a larger group than XYP, therefore there is more information about them than about the XYP subfamily. [3]
CDPS-encoding genes are found in genomic locations with genes encoding additional biosynthetic enzymes (CDPS DmtB1 is an example, encoded by the gene of dmt1 locus). These additional biosynthetic enzymes are for example: oxidoreductases, prenyltransferases, methyltransferases, or cyclases and some proteins as cytochrome P450s. [13] [14]
Recently bioinformatics are designing a way to predict CDPSs products to understand better how their catalytic process works. Moreover, research has brought to light a lot of chemical information about CDPSs pathways. Different projects can also create chemical diversity. [13]
The importance of the cyclodipeptides production has attracted immense attention because of their properties, not only as antifungal or antibacterial but also as a biological target. That is why an important part of the pharmaceutical products contain CDPs. [13] [4]
In elongation reference, go for "Part of transcription of DNA into mRNA".
Pyrrolysine is an α-amino acid that is used in the biosynthesis of proteins in some methanogenic archaea and bacteria; it is not present in humans. It contains an α-amino group, a carboxylic acid group. Its pyrroline side-chain is similar to that of lysine in being basic and positively charged at neutral pH.
An aminoacyl-tRNA synthetase, also called tRNA-ligase, is an enzyme that attaches the appropriate amino acid onto its corresponding tRNA. It does so by catalyzing the transesterification of a specific cognate amino acid or its precursor to one of all its compatible cognate tRNAs to form an aminoacyl-tRNA. In humans, the 20 different types of aa-tRNA are made by the 20 different aminoacyl-tRNA synthetases, one for each amino acid of the genetic code.
In molecular biology, biosynthesis is a multi-step, enzyme-catalyzed process where substrates are converted into more complex products in living organisms. In biosynthesis, simple compounds are modified, converted into other compounds, or joined to form macromolecules. This process often consists of metabolic pathways. Some of these biosynthetic pathways are located within a single cellular organelle, while others involve enzymes that are located within multiple cellular organelles. Examples of these biosynthetic pathways include the production of lipid membrane components and nucleotides. Biosynthesis is usually synonymous with anabolism.
Aminoacyl-tRNA is tRNA to which its cognate amino acid is chemically bonded (charged). The aa-tRNA, along with particular elongation factors, deliver the amino acid to the ribosome for incorporation into the polypeptide chain that is being produced during translation.
Tyrocidine is a mixture of cyclic decapeptides produced by the bacteria Brevibacillus brevis found in soil. It can be composed of 4 different amino acid sequences, giving tyrocidine A–D. Tyrocidine is the major constituent of tyrothricin, which also contains gramicidin. Tyrocidine was the first commercially available antibiotic, but has been found to be toxic toward human blood and reproductive cells. The function of tyrocidine within its host B. brevis is thought to be regulation of sporulation.
In enzymology, an alanine—tRNA ligase is an enzyme that catalyzes the chemical reaction
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In enzymology, a phenylalanine—tRNA ligase is an enzyme that catalyzes the chemical reaction
In enzymology, a trypanothione synthase (EC 6.3.1.9) is an enzyme that catalyzes the chemical reaction
Tyrosine—tRNA ligase, also known as tyrosyl-tRNA synthetase is an enzyme that is encoded by the gene YARS. Tyrosine—tRNA ligase catalyzes the chemical reaction
Tyrosyl-tRNA synthetase, cytoplasmic, also known as Tyrosine-tRNA ligase, is an enzyme that in humans is encoded by the YARS gene.
Bifunctional aminoacyl-tRNA synthetase is an enzyme that in humans is encoded by the EPRS gene.
Arginyl-tRNA synthetase, cytoplasmic is an enzyme that in humans is encoded by the RARS gene.
Glutaminyl-tRNA synthetase is an enzyme that in humans is encoded by the QARS gene.
SARS and cytoplasmic seryl-tRNA synthetase are a human gene and its encoded enzyme product, respectively. SARS belongs to the class II amino-acyl tRNA family and is found in all humans; its encoded enzyme, seryl-tRNA synthetase, is involved in protein translation and is related to several bacterial and yeast counterparts.
Phenylalanyl-tRNA synthetase alpha chain is an enzyme that in humans is encoded by the FARSA gene.
Amino acid activation refers to the attachment of an amino acid to its respective transfer RNA (tRNA). The reaction occurs in the cell cytosol and consists of two steps: first, the enzyme aminoacyl tRNA synthetase catalyzes the binding of adenosine triphosphate (ATP) to a corresponding amino acid, forming a reactive aminoacyl adenylate intermediate and releasing inorganic pyrophosphate (PPi). Subsequently, aminoacyl tRNA synthetase binds the AMP-amino acid to a tRNA molecule, releasing AMP and attaching the amino acid to the tRNA. The resulting aminoacyl-tRNA is said to be charged.
The aminoacyl-tRNA synthetases catalyse the attachment of an amino acid to its cognate transfer RNA molecule in a highly specific two-step reaction. These proteins differ widely in size and oligomeric state, and have limited sequence homology. The 20 aminoacyl-tRNA synthetases are divided into two classes, I and II. Class I aminoacyl-tRNA synthetases contain a characteristic Rossmann fold catalytic domain and are mostly monomeric. Class II aminoacyl-tRNA synthetases share an anti-parallel beta-sheet fold flanked by alpha-helices, and are mostly dimeric or multimeric, containing at least three conserved regions. However, tRNA binding involves an alpha-helical structure that is conserved between class I and class II synthetases. In reactions catalysed by the class I aminoacyl-tRNA synthetases, the aminoacyl group is coupled to the 2'-hydroxyl of the tRNA, while, in class II reactions, the 3'-hydroxyl site is preferred. The synthetases specific for arginine, cysteine, glutamic acid, glutamine, isoleucine, leucine, methionine, tyrosine, tryptophan and valine belong to class I synthetases; these synthetases are further divided into three subclasses, a, b and c, according to sequence homology. The synthetases specific for alanine, asparagine, aspartic acid, glycine, histidine, lysine, phenylalanine, proline, serine, and threonine belong to class-II synthetases.
Polyprenyl synthetases are a class of enzymes responsible for synthesis of isoprenoids. Isoprenoid compounds are synthesized by various organisms. For example, in eukaryotes the isoprenoid biosynthetic pathway is responsible for the synthesis of a variety of end products including cholesterol, dolichol, ubiquinone or coenzyme Q. In bacteria this pathway leads to the synthesis of isopentenyl tRNA, isoprenoid quinones, and sugar carrier lipids. Among the enzymes that participate in that pathway, are a number of polyprenyl synthetase enzymes which catalyze a 1'4-condensation between 5-carbon isoprene units. It has been shown that all the above enzymes share some regions of sequence similarity. Two of these regions are rich in aspartic-acid residues and could be involved in the catalytic mechanism and/or the binding of the substrates.
Drimentine G belongs to the family of drimentines, which are terpenylated diketopiperazines. As the name suggests, DMT G contains two different parts, one comes from the non-ribosomal peptide synthetase (NRPS) pathway to generate the diketopiperazine ring structure. The other part comes from either the mevalonic acid pathway (MVA) or deoxy xylulose phosphate pathway (MEP) to produce sesquiterpenes needed for interaction with the diketopiperazine. This molecule is said to be useful as an antibiotic to treat bacterial or fungi infections, has therapeutic application to treat animal health, and can serve as a pest control for plants.
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