Catalysis by a rigid enzyme

Abstract

AbstractMany enzymes are dynamic entities, sampling conformational states that are relevant for catalytic activity. Crystal structures of catalytic intermediates suggest, however, that not all enzymes require structural changes for activity. The single-domain enzyme xylanase fromBacillus circulans(BCX) is involved in the degradation of hemicellulose. We demonstrate that BCX in solution undergoes minimal structural changes during catalysis. NMR spectroscopy results show that the rigid protein matrix provides a frame for fast substrate binding in multiple conformations, accompanied by slow, enzyme induced substrate distortion. Therefore, we propose a model in which the rigid enzyme takes advantage of substrate flexibility to induce a conformation that facilitates catalysis.One Sentence SummaryThe rigid matrix of BCX uses substrate flexibility in Michaelis complex formation.