Abstract

Peptide histidine-isoleucine (PH I) and its human analogue peptide histidine-methionine (PHM) are members of a superfamily of structurally related peptides embracing, among others, pituitary adenylate cyclase-activating polypeptide (PACAP), vasoactive intestinal peptide (VIP), peptide histidine-valine (PHV), and helodermin. All the peptides display a pleiotropic biological activity. PHI, PHM, PHV and VIP are co-synthesized from the same precursor and share high levels of structural and functional similarity. These peptides may act through common receptors and are widely distributed throughout the body tissues (the central nervous system, gastrointestinal tract, respiratory system, and reproductive system); however, their role remains largely unknown. Changes in the levels of the peptides in the course of different diseases suggest their possible importance and usefulness in diagnostics. Moreover, the neurotrophic and neuroprotective properties of PHI suggest, by analogy to VIP or PACAP, its therapeutic potential in many neurodegenerative diseases, such as Alzheimer’s and Parkinson’s disease.

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