Hatano Ken-ichi, Sawano Yoriko, Tanokura Masaru
Department of Biological Sciences, Faculty of Engineering, Gunma University, Kiryu, Japan.
Biol Chem. 2002 Jul-Aug;383(7-8):1151-6. doi: 10.1515/BC.2002.126.
Bromelain isoinhibitors from pineapple stem (BIs) are unique double-chain inhibitors and inhibit the cysteine proteinase bromelain competitively. The three-dimensional structure was shown to be composed of two distinct domains, each of which is formed by a three-stranded anti-parallel beta-sheet. Unexpectedly, BIs were found to share similar folding and disulfide-bond connectivities not with the cystatin superfamily, but with Bowman-Birk trypsin/chymotrypsin inhibitor (BBI). The structural similarity between them suggests that BIs and BBI have evolved from a common ancestor and differentiated in function during the course of molecular evolution.
