Biomedical Importance (Amino Acids and Proteins): BioRat Biochemistry Blog www.biorat.blogspot.com

Biomedical Importance (Amino Acids and Proteins): BioRat Biochemistry Blog www.biorat.blogspot.com

Biomedical Importance In addition to providing the monomer units from which the long polypeptide chains of proteins are synthesized, the L -a-amino acids and their derivatives participate in cellular functions as diverse as nerve transmission and the biosynthesis of porphyrins, purines, pyrimidines, and urea. Short polymers of amino acids called peptides  perform prominent roles in the neuroendocrine system as hormones, hormone-releasing factors, neuromodulators, or neurotransmitters. While proteins contain only L-a-amino acids, microorganisms elaborate peptides that contain both D- and L-a-amino acids. Several of these peptides are of therapeutic value, including the antibiotics bacitracin and gramicidin A and the antitumor agent bleomycin. Certain other microbial peptides are toxic. The cyanobacterial peptides microcystin and nodularin are lethal in large doses, while small quantities promote the formation of hepatic tumors. Humans and other higher animals lack the capability to synthesize 10 of the 20 common L-a-amino acids in amounts adequate to support infant growth or to maintain health in adults. Consequently, the human diet must contain adequate quantities of these nutritionally essential amino acids.

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