Abstract
The freshwater cyanobacterium Planktothrix rubescens produces the cyclooctapeptide cyclo(Pro-Gly-Leu-Val-Met-Phe-Gly-Val). The chemical structure is new. This homodetic cyclic octapeptide was named planktocyclin ( 1). It consists solely of proteinogenic l-amino acids and is a strong inhibitor of mammalian trypsin and alpha-chymotrypsin and a moderately active inhibitor of human recombinant caspase-8. Mass spectrometric and 2D-NMR spectroscopic data allowed the determination of its structure. Synthetic planktocyclin was identical to the natural product.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Sequence
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Amino Acids / chemistry
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Animals
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Caspase Inhibitors
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Cattle
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Chymotrypsin / antagonists & inhibitors*
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Cyanobacteria / chemistry*
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Fresh Water
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Humans
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Molecular Structure
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Nuclear Magnetic Resonance, Biomolecular
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Peptides, Cyclic / chemistry
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Peptides, Cyclic / isolation & purification*
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Peptides, Cyclic / pharmacology*
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Protease Inhibitors / chemistry
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Protease Inhibitors / isolation & purification*
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Protease Inhibitors / pharmacology
Substances
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Amino Acids
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Caspase Inhibitors
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Peptides, Cyclic
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Protease Inhibitors
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planktocyclin
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Chymotrypsin
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alpha-chymotrypsin