title: Recombinant pro-regions from papain and papaya proteinase IV-are selective high affinity inhibitors of the mature papaya enzymes.
abstract: Proteolytic enzymes require the presence of their pro-regions for correct folding. Of the four proteolytic enzymes from Carica papaya, papain and papaya proteinase IV (PPIV) have 68% sequence identity. We find that their pro-regions are even more similar, exhibiting 73.6% identity. cDNAs encoding the pro-regions of these two proteinases have been expressed in Escherichia coli independently from their mature enzymes. The recombinant pro-regions of papain and PPIV have been shown to be high affinity inhibitors of all four of the mature native papaya cysteine proteinases. Their inhibition constants are in the range 10(-6) - 10(-9) M. PPIV was inhibited two to three orders of magnitude less effectively than papain, chymopapain and caricain. The pro-region of PPIV, however, inhibited its own mature enzyme more effectively than did the pro-region of papain. Alignment of the sequences of the four papaya enzymes shows that there is a highly variable section towards the C-terminal of the pro-region. This region may therefore confer selectivity to the pro-regions for the individual proteolytic enzymes.
authors.affiliation: Protein Engineering Department, Institute of Food Research, Reading, UK.
authors.forename: M A
authors.initials: MA
authors.lastname: Taylor
authors.forename: K C
authors.initials: KC
authors.lastname: Baker
authors.forename: G S
authors.initials: GS
authors.lastname: Briggs
authors.forename: I F
authors.initials: IF
authors.lastname: Connerton
authors.forename: N J
authors.initials: NJ
authors.lastname: Cummings
authors.forename: K A
authors.initials: KA
authors.lastname: Pratt
authors.forename: D F
authors.initials: DF
authors.lastname: Revell
authors.forename: R B
authors.initials: RB
authors.lastname: Freedman
authors.forename: P W
authors.initials: PW
authors.lastname: Goodenough
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D003546:Cysteine Endopeptidases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D015853:Cysteine Proteinase Inhibitors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D004792:Enzyme Precursors / Q000737:chemistry* / Q000235:genetics; D015870:Gene Expression; D007700:Kinetics; D008969:Molecular Sequence Data; D010206:Papain / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology; D011485:Protein Binding; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
chemical_list: D015853:Cysteine Proteinase Inhibitors; D004792:Enzyme Precursors; D010446:Peptide Fragments; D011994:Recombinant Proteins; D003546:Cysteine Endopeptidases; D010206:Papain; C050874:glycyl endopeptidase