Read it for yourself.
Posted by Earl on another site. If you believe that bacteria in a dog's gut is capable of synthesising dermorphin, then the greyhound industry is done for. The heading clearly says Dermorphin production by bacteria. Nothing to do with nobbling.
Dermorphin Production by Bacteria
Distinct pathways for modification of the bacterial cell wall by non-canonical D-amino acids
Non canonical amino acids are amino acids that are not one of the 20 amino acids normally found in structural proteins in animals.
L,D-transpeptidases incorporate non-canonical D-amino acids into tetrapeptides of V. cholerae PG.
The difference between efficiencies for the forward (D-Ala → D-Met) and reverse (D-Met → D-Ala) reactions suggests that accumulation of D-Met muropeptides would be favoured in vivo, even if both D-Met and D-Ala were simultaneously present at similar concentrations. Therefore, in stationary phase, when D-Met is present, LdtA is likely to promote accumulation of muro4M peptides, rather than a continual exchange of the C-terminal amino acid within tetrapeptides.
Muro4 peptides are tetrapeptides used in the formation of bacterial cell walls.
In natural environments, bacterial communities typically contain multiple species (Straight and Kolter, 2009), which could produce a variety of D-amino acids (Lam et al, 2009)
The D-amino acid in Dermorphin is D-Arginine which according to the above article could possibly be produced by naturally occurring bacterial communities, eg, in the intestine.
Different processes control formation of D-Met muropeptides in bacteria
To begin to explore whether the pathways for incorporation of NCDAAs are conserved, we assessed whether D-Met was targeted to equivalent muropeptides within diverse species, and whether mutations and antibiotics have uniform effects upon D-Met incorporation. Unexpectedly, these assays revealed that only V. cholerae and C. crescentus incorporate NCDAAs into both tetrapeptides and pentapeptides, although C. crescentus, unlike V. cholerae, contains predominantly muro5M (Figure 4D; Supplementary Figure S1). PG from all other organisms tested contained just one of the two classes of peptides. Following growth in media supplemented with D-Met, muro4M peptides were detected in PG from E. coli and P. aeruginosa, while muro5M peptides were detected in PG from B. subtilis, E. faecalis and S. aureus (Figure 4D;
E.coli is a naturally occuring bacteria in mammalian intestines.
NCDAAs, such as D-Met, are incorporated at two distinct sites within V. cholerae PG subunits. The majority of D-Met (80%) is present as the C-terminal amino acid within monomeric or dimeric tetramers (muro4M), while the remainder comprises the C-terminal amino acid within pentapeptides (muro5M). Formation of muro4M peptides is dependent upon Ldts, inner membrane-anchored periplasmic proteins that catalyse L,D crosslinking of muropeptides and linkage of lipoprotein Lpp to PG (Magnet et al, 2007b,
In vitro characterization of a purified Ldt from V. cholerae (LdtA) revealed that it can exchange the C-terminal amino acid of a variety of tetrapeptide substrates. However, LdtA is more efficient at catalysing exchange in dimeric than in monomeric substrates, and it more readily catalyses replacement of D-Ala by D-Met than the reverse reaction. The latter finding indicates that LdtA should promote muro4M accumulation in stationary phase, when NCDAAs are produced. LdtA can accept many D-amino acids as substrates, a flexibility that may enable reaction to the range of D-amino acids produced during stationary phase by diverse organisms in the natural environment.
Tetrapeptide formation incorporating D-amino acids can occur naturally with a variety of tetrapeptides able to be formed.
Peptidoglycan is a polysaccharide made of two glucose derivatives, N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM), alternated in long chains. The chains are cross-linked to one another by a tetrapeptide that extends off the NAM sugar unit, allowing a lattice-like structure to form. The four amino acids that compose the tetrapeptide are: L-alanine, D-glutamine, L-lysine or meso-diaminopimelic acid (DPA), and D-alanine. Typically only the L-isomeric form of amino acids are utilized by cells but the use of the mirror image D-amino acids provides protection from proteases that might compromise the integrity of the cell wall by attacking the peptidoglycan. The tetrapeptides can be directly cross-linked to one another, with the D-alanine on one tetrapeptide binding to the L-lysine/ DPA on another tetrapeptide.
Tetrapeptides are naturally produced in large quantities for bacterial cell wall production with D-amino acids typically incorporated .
Octapeptides synthesized from D amino acids were absorbed from the intestine and excreted in urine of normal rats drinking 5% glucose/1% creatinine containing the 125I-labeled peptides at 0.1-25 mg/dl
Octapeptides being considerably larger and more complex than tetrapeptides, it is reasonable to assume that tetrapeptides would also be absorbed from the mammalian intestine.
The main structural features of the cell wall peptidoglycan of E.coli B have been established by Weidel and co-workers. According to these authors the principal repeating unit in this peptidoglycan is represented by the disaccharide tetrapeptide GNAc-MurNAc-L-Ala-D-Glu-meso-DAP-D-Ala.
Tetrapeptides being an integral part of bacterial cell walls would naturally be released into the intestine upon death and breakdown of the bacteria. Absorption of some of these breakdown products is entirely logical.
Preprodermaseptin b and preproadenoregulin have considerable sequence identities to the precursors encoding the opioid heptapeptides dermorphin, dermenkephalin, and deltorphins
The hyperdivergence of modern antimicrobial peptides and the number of peptides per species result from repeated duplications of an approximately 150-million-year-old ancestral gene and accelerated mutations of the mature peptide domain, probably involving a mutagenic, error-prone, DNA polymerase similar to Escherichia coli Pol V.
Although many of the peptides produced by frogs are antibacterial, they are produced by a similar gene in E.coli which has the ability to produce a variety of tetrapeptides.
No work appears to have been on whether E.coli or other intestinal bacteria can produce the tetrapeptide sequence for dermorphin but it seems entirely logical that this is possible.
Dermorphin is not found in humans or other mammals and similar D-amino acid peptides have only been found in bacteria, amphibians and molluscs. Dermorphin appears to be made in these through an unusual posttranslational modification carried out by an amino acid isomerase. This unusual process is needed because the D-alanine in this peptide is not among the 20 amino acids coded for in the genetic code and thus the peptide cannot be synthesized in the usual way from the encodings in the genome of an organism.
An isomerase is a specific enzyme capable of transforming an L-Amino acid into a D-Amino acid.
I didn't make this up. You all have a nice day.