Influence of the conformational flexibility on the kinetics and dimerisation process of two Candida rugosa lipase isoenzymes

We have investigated the interfacial activation process of two isoenzymes f rom Candida rugosa (Lip1 and Lip3) using triacetin as substrate. Kinetics w ere coupled to inhibition experiments in order to analyse the transition be tween the open and closed conformers. This process was slow, particularly f or Lip1, in the absence of an interface provided by the substrate or a dete rgent. Dimers of Lip3 were also purified and their catalytic action was clo ser to that of a typical esterase, In spite of the high sequence homology b etween Lip1 and Lip3, small changes enhance hydrophobicity in the binding p ocket of Lip3 and increase the flexibility of its flap. We postulated that these factors account for the higher tendency of Lip3 to dimerise fixing it s open conformation. (C) 2001 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies.