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D-ENZYMES. "When Sir Hans Krebs accidentally discovered an enzyme from kidney that recognized ‘non-natural’ D-amino acids (but not their L-counterparts), it was not clear why nature would have created such an enzyme." https://lnkd.in/etGHsGm View in LinkedIn

WHY IS THE UNNATURAL AMINO ACID IN BRAIN? "What about the metabolism of d-serine made in the brain? Here, the d-serine is produced mainly or exclusively in the cytosolic matrix of astroglia, which occur in close vicinity to NMDA receptors in the synapse-rich grey matter." https://lnkd.in/etGHsGm View in LinkedIn

HEPATIC SOURCE? "D-Serine is also found in the serum, and the likely source for this D-serine is hepatic, because liver is the only other tissue besides brain that expresses appreciable levels of serine racemase." https://lnkd.in/etGHsGm View in LinkedIn

BACTERIAL SIMILARITY. "Mammalian serine racemase most closely resembles prokaryotic serine and threonine dehydratases...one cannot put a very precise date on when d-serine synthesis arose in eukaryotes." https://lnkd.in/etGHsGm View in LinkedIn

CONVERGENT EVOLUTION. "The cytosolic serine racemase of mammals...is likely to be an example of convergent evolution: it catalyses a reaction similar to the alanine racemase in bacteria, but this activity has evolved independently via a separate protein lineage, and probably emerged long after the divergence of prokaryotes and eukaryotes." https://lnkd.in/etGHsGm View in LinkedIn

SECOND GLANCE. "However, the bacterial proteins with the greatest amino acid similarity to mammalian serine racemase are not racemases at all but rather serine/threonine dehydratases, which also use B6." https://lnkd.in/etGHsGm View in LinkedIn

"AT FIRST GLANCE it might seem that the serine racemase of mammals has evolved from the alanine racemase of prokaryotes, because the two enzymes use the same cofactor to catalyse closely related reactions." https://lnkd.in/etGHsGm View in LinkedIn

D-AMINO ACID CELL WALLS. "Prokaryotic genomes contain a variety of amino acid racemases which produce d-amino acid substrates for incorporation into the cell wall peptidoglycan via the action of d-amino acid transaminase, an enzyme found only in bacteria." https://lnkd.in/etGHsGm View in LinkedIn

ANCIENT ORIGINS. "The concept of treating fecal diseases with fecal matter originated in China millennia ago. Fourth century Chinese medical literature mentions it to treat food poisoning and severe diarrhea." https://lnkd.in/e4DWYcp View in LinkedIn

NMDA RECEPTOR in the mammalian brain is susceptible to cytotoxicity and is involved in seizures, pain and various neurological disorders, via glutamate, and as such is a major drug target. It is key to memory and learning among other important functions. https://lnkd.in/edHFErG View in LinkedIn