Expression of a functional proteinase inhibitor capable of accepting xylose: bikunin

Research output: Contribution to journalArticle


Bikunin is a Kunitz-type proteinase inhibitor, which is cross-linked to heavy chains via a chondroitin sulfate chain, forming inter-alpha-inhibitor and related molecules. Rat bikunin was produced by baculovirus-infected insect cells. The protein could be purified with a total yield of 20 mg/liter medium. Unlike naturally occuring bikunin the recombinant protein had no galactosaminoglycan chain. Endoglycosidase digestion also suggested that the recombinant form lacked N-linked oligosaccharides. Bikunin is translated as a part of a precursor, alpha1-microglobulin/bikunin, but the functional significance of the cotranslation is unknown. Our results indicate that the proteinase inhibitory function of bikunin is not regulated by the alpha1-microglobulin-part of the alpha1-microglobulin/bikunin precursor since recombinant bikunin had the same trypsin inhibitory activity as the recombinant precursor. Both free bikunin and the precursor were also functional as a substrate in an in vitro xylosylation system. This demonstrates that the alpha1-microglobulin-part is not necessary for the first step of galactosaminoglycan assembly.


Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Infectious Medicine
  • Cancer and Oncology
  • Cell and Molecular Biology
  • Immunology in the medical area


  • bikunin, greek small letter alpha1-microglobulin/bikunin precursor, proteinase inhibition, xylosylation, insect cells
Original languageEnglish
Pages (from-to)99-106
JournalArchives of Biochemistry and Biophysics
Issue number1
Publication statusPublished - 2001
Publication categoryResearch

Bibliographic note

The information about affiliations in this record was updated in December 2015. The record was previously connected to the following departments: Oncology, MV (013035000), Medical Inflammation Research (013212019), Matrix biology (013212025), Division of Infection Medicine (BMC) (013024020), Department of Experimental Medical Science (013210000)