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Ergocryptine is an
The next step in the biosynthesis of ergocryptine is the transformation of 4-dimethylallyl abrine to Chanoclavine-I. It has been shown that the enzymes EasE and EasC (FgaOx1 and FgaCat in A. fumigatus, respectively) are both required to generate Chanoclavine-I from 4-DMA abrine. Mutation experiments altering these enzymes independently stopped the pathway at abrine. This indicates that cooperation between EasE and EasC is necessary.
Chanocalvine-I is then oxidized to chanoclavine-I aldehyde with NAD+ dependent enzyme EasD (FgaDH in A. fumigatus). Chanoclavine-I aldehyde is a branch point, leading to different ergot alkaloids, depending on the specific fungus. In C. purpurea, chanoclavine-I aldehyde is converted to argoclavine with EasA, referred to as the old yellow enzyme or FgaOx3. This process occurs via keto-enol tautomerization to facilitate rotation about a carbon-carbon bond, followed by tautomerization back to the aldehyde, and condensation with the proximal secondary amine. The iminium species created by cyclization is then reduced to the tertiary amine, yielding agroclavine.
A cyctochrome P-450 monooxygenase enzyme catalyzes a two electron oxidation of agroclavne to the corresponding primary alcohol, elymoclavine. Elymoclavine is then oxidized by four electrons by a P450 monooxygenase to give paspalic acid. Paspalic acid then undergoes isomerization of the carbon-carbon double bond that is in conjugation with the acid, to give D-lysergic acid.
Lysergic Acid is a branch point in the biosynthesis of ergoamides and ergopeptines. On the path to ergocryptine, an ergopeptine, the tripeptide is installed by a Non-Ribosomal Peptide Synthase (NRPS). It has been shown that there are two enzymes, D-lysergyl peptide synthases (LPS) 1 and 2, which are responsible for the tripeptide connection to lysergic acid. The timing of the oxidation of valine to an alcohol is not exactly known. However, it is speculated that the oxidation occurs while bound to the NRPS LPS2. Ergocryptine is found in two forms, differing in the amino acid used by the NRPS. The alpha form contains the amino acid leucine, while the beta-form uses the amino acid isoleucine.
ergopeptine
Ergoline is a chemical compound whose structural skeleton is contained in a variety of alkaloids, referred to as ergoline derivatives or ergoline alkaloids. Ergoline alkaloids, one being ergine, were initially characterized in ergot. Some of thes ...
and one of the ergot
Ergot ( ) or ergot fungi refers to a group of fungi of the genus ''Claviceps''.
The most prominent member of this group is ''Claviceps purpurea'' ("rye ergot fungus"). This fungus grows on rye and related plants, and produces alkaloids that ca ...
alkaloid
Alkaloids are a class of basic, naturally occurring organic compounds that contain at least one nitrogen atom. This group also includes some related compounds with neutral and even weakly acidic properties. Some synthetic compounds of similar ...
s. It is isolated from ergot or fermentation broth and it serves as starting material for the production of bromocriptine
Bromocriptine, originally marketed as Parlodel and subsequently under many brand names, is an ergoline derivative and dopamine agonist that is used in the treatment of pituitary tumors, Parkinson's disease, hyperprolactinaemia, neuroleptic maligna ...
.
Chemistry
Ergocryptine is a mixture of two very similar compounds, ''alpha-'' and ''beta''-ergocryptine. The ''beta'' differs from the ''alpha'' form only in the position of a singlemethyl
In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula . In formulas, the group is often abbreviated as Me. This hydrocarbon group occurs in many ...
group, which is a consequence of the biosynthesis
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. ...
in which the proteinogenic amino acid
Proteinogenic amino acids are amino acids that are incorporated biosynthetically into proteins during translation. The word "proteinogenic" means "protein creating". Throughout known life, there are 22 genetically encoded (proteinogenic) amino aci ...
leucine
Leucine (symbol Leu or L) is an essential amino acid that is used in the biosynthesis of proteins. Leucine is an α-amino acid, meaning it contains an α-amino group (which is in the protonated −NH3+ form under biological conditions), an α- ca ...
is replaced by isoleucine
Isoleucine (symbol Ile or I) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated −NH form under biological conditions), an α-carboxylic acid group (which is in the deprot ...
.
Biosynthesis
The biosynthetic pathways to ergocryptine starts with the prenylation of L-tryptophan in an SN1 fashion with Dimethylallylpyrophosphate (DMAPP). The DMAPP is derived from Mevalonic Acid. This reaction is catalyzed by a prenyltransferase enzyme (Prenyltransferase 4-dimethylallyltryptophan synthase) named FgaPT2 in A. fumigatus. An X-ray structure of the prenyltransferase FgaPT2 and tryptophan has been reported, and used to propose a three step mechanism (formation of allylic carbocation, nucleophilic attack of tryptophan on the carbocation, then deprotonation to restore aromaticity and generate the product, 4-dimethylallyltryptophan (DMAT)). DMAT is then N-methylated at the amino of the tryptophan backbone with the EasF enzyme, named FgaMT in A. fumigatus. S-adenosylmethionine (SAM) being the methyl source.
The next step in the biosynthesis of ergocryptine is the transformation of 4-dimethylallyl abrine to Chanoclavine-I. It has been shown that the enzymes EasE and EasC (FgaOx1 and FgaCat in A. fumigatus, respectively) are both required to generate Chanoclavine-I from 4-DMA abrine. Mutation experiments altering these enzymes independently stopped the pathway at abrine. This indicates that cooperation between EasE and EasC is necessary.
Chanocalvine-I is then oxidized to chanoclavine-I aldehyde with NAD+ dependent enzyme EasD (FgaDH in A. fumigatus). Chanoclavine-I aldehyde is a branch point, leading to different ergot alkaloids, depending on the specific fungus. In C. purpurea, chanoclavine-I aldehyde is converted to argoclavine with EasA, referred to as the old yellow enzyme or FgaOx3. This process occurs via keto-enol tautomerization to facilitate rotation about a carbon-carbon bond, followed by tautomerization back to the aldehyde, and condensation with the proximal secondary amine. The iminium species created by cyclization is then reduced to the tertiary amine, yielding agroclavine.
A cyctochrome P-450 monooxygenase enzyme catalyzes a two electron oxidation of agroclavne to the corresponding primary alcohol, elymoclavine. Elymoclavine is then oxidized by four electrons by a P450 monooxygenase to give paspalic acid. Paspalic acid then undergoes isomerization of the carbon-carbon double bond that is in conjugation with the acid, to give D-lysergic acid.
Lysergic Acid is a branch point in the biosynthesis of ergoamides and ergopeptines. On the path to ergocryptine, an ergopeptine, the tripeptide is installed by a Non-Ribosomal Peptide Synthase (NRPS). It has been shown that there are two enzymes, D-lysergyl peptide synthases (LPS) 1 and 2, which are responsible for the tripeptide connection to lysergic acid. The timing of the oxidation of valine to an alcohol is not exactly known. However, it is speculated that the oxidation occurs while bound to the NRPS LPS2. Ergocryptine is found in two forms, differing in the amino acid used by the NRPS. The alpha form contains the amino acid leucine, while the beta-form uses the amino acid isoleucine.
See also
* DihydroergocryptineReferences
{{Ergolines Ergot alkaloids Lactams Oxazolopyrrolopyrazines