N- and C-terminal region mediated oligomerization of the cyclodextrin-/pullulan degrading enzymes

Abstract

Cyclodextrin-/pullulan (CD-/PUL)-degrading enzymes catalyze hydrolysis and transglycosylation reactions of various substrates such as starch, cyclodextrin, and pullulan. Recently, these enzymes have been proved to exist in equilibria of monomer-dimer and monomer-dimer-tetramer or -dodecamer. Two regions in the CD-/PUL-degrading enzymes were identified as being involved in oligomerization; one is close to the N-terminal and the other located near the C-terminal region. The three-dimensional structure and deletion mutagenesis analyses revealed that the N-terminal region affected the dimerization properties of monomeric Thermus maltogenic amylase (ThMA). On the other hand, both the N- and C-terminal regions were involved in dodecamerization of cyclodextrinase I-5 (CDase I-5) dimeric units. Oligomerization of these enzymes was also modulated by salt concentration and pH of the reaction buffer.