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  • Title: A Peptide-Induced Self-Cleavage Reaction Initiates the Activation of Tyrosinase.
    Author: Kampatsikas I, Bijelic A, Pretzler M, Rompel A.
    Journal: Angew Chem Int Ed Engl; 2019 May 27; 58(22):7475-7479. PubMed ID: 30825403.
    Abstract:
    The conversion of inactive pro-polyphenol oxidases (pro-PPOs) into the active enzyme results from the proteolytic cleavage of its C-terminal domain. Herein, a peptide-mediated cleavage process that activates pro-MdPPO1 (Malus domestica) is reported. Mass spectrometry, mutagenesis studies, and X-ray crystal-structure analysis of pro-MdPPO1 (1.35 Å) and two separated C-terminal domains, one obtained upon self-cleavage of pro-MdPPO1 and the other one produced independently, were applied to study the observed self-cleavage. The sequence Lys 355-Val 370 located in the linker between the active and the C-terminal domain is indispensable for the self-cleavage. Partial introduction (Lys 352-Ala 360) of this peptide into the sequence of two other PPOs, MdPPO2 and aurone synthase (CgAUS1), triggered self-cleavage in the resulting mutants. This is the first experimental proof of a self-cleavage-inducing peptide in PPOs, unveiling a new mode of activation for this enzyme class that is independent of any external protease.
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