Cyclo(His-Pro): its distribution, origin and function in the human.
Cyclo(His-Pro), or histidyl-proline diketopiperazine, is a cyclic dipeptide endogenous to blood, cerebrospinal fluid (CSF), semen, brain, spinal cord, and gastrointestinal tract of humans. Although a part of cyclo(His-Pro) clearly appears to be derived from the limited proteolysis of thyrotropin-releasing hormone by Pyroglutamate aminopeptidase, the biosynthetic origin of the remainder of the peptide can only be speculated. The levels of this peptide in blood and CSF fluctuate in health and disease in a manner appropriate for a physiologically active endogenous molecule.
Prasad
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Department of Medicine, Louisiana State University Medical Center, New Orleans 70112.
D002490:Central Nervous System / Q000032:analysis*; D004064:Digestive System / Q000032:analysis*; D006801:Humans; D009928:Organ Specificity; D010456:Peptides, Cyclic / Q000032:analysis / Q000502:physiology*; D010879:Piperazines / Q000032:analysis / Q000502:physiology*
D010456:Peptides, Cyclic; D010879:Piperazines; C015924:histidyl-proline diketopiperazine