An immune-responsive Serpin regulates the melanization cascade in Drosophila

Dev Cell. 2002 Oct;3(4):581-92. doi: 10.1016/s1534-5807(02)00267-8.


In arthropods, the melanization reaction is associated with multiple host defense mechanisms leading to the sequestration and killing of invading microorganisms. Arthropod melanization is controlled by a cascade of serine proteases that ultimately activates the enzyme prophenoloxidase (PPO), which, in turn, catalyzes the synthesis of melanin. Here we report the biochemical and genetic characterization of a Drosophila serine protease inhibitor protein, Serpin-27A, which regulates the melanization cascade through the specific inhibition of the terminal protease prophenoloxidase-activating enzyme. Our data demonstrate that Serpin-27A is required to restrict the phenoloxidase activity to the site of injury or infection, preventing the insect from excessive melanization.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Catechol Oxidase / immunology
  • Catechol Oxidase / metabolism
  • Drosophila Proteins / genetics
  • Drosophila Proteins / immunology*
  • Drosophila melanogaster / genetics
  • Drosophila melanogaster / immunology*
  • Enzyme Precursors / immunology
  • Enzyme Precursors / metabolism
  • Melanins / immunology
  • Melanins / metabolism
  • Molecular Sequence Data
  • Mutation
  • Serpins / genetics
  • Serpins / immunology*
  • Signal Transduction / immunology


  • Drosophila Proteins
  • Enzyme Precursors
  • Melanins
  • Serpins
  • Spn27A protein, Drosophila
  • pro-phenoloxidase
  • Catechol Oxidase