A Peptide-Induced Self-Cleavage Reaction Initiates the Activation of Tyrosinase.

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.

SUBMITTER: Kampatsikas I 

PROVIDER: S-EPMC6563526 | biostudies-literature | 2019 May

REPOSITORIES: biostudies-literature