Vioserpin, a serine protease inhibitor from Gloeobacter violaceus possibly regulated by heparin

Serine peptidase inhibitor (serpin) is the name given to the superfamily of proteins with wide range of biological functions, and that the main feature is the inhibition of serine proteases. Here we describe the inhibitory characterization of a serpin from Gloeobacter violaceus that we named vioserpin. The serpin presented a high specificity to inhibit trypsin-like enzymes with a rapid inhibition rate constant (2.1 × 106 M−1 s−1). We also demonstrated that the inhibitory activity of the vioserpin is influenced by the concentration of heparin, and this finding may throw a new light on understanding the molecular evolution of serpins. •Biochemical characterization of the vioserpin, a serine protease inhibitor from the bacteria Gloeobacter violaceus•The vioserpin inhibits specifically trypsin-like enzymes, with a very high second-order rate constant.•Vioserpin is modulated by glycosaminoglycans, a characteristic found in serpins from eukaryotic organisms only.•The phylogenetic studies point for a new branch of the serpin superfamily in prokaryotes.