Lipases at interfaces

Doctoral thesis, 2008

Lipases are acyl hydrolases that play a key role in fat digestion by cleaving long-chain triglycerides into polar lipids. Due to an opposite polarity between the enzyme (is hydrophilic) and their substrates (are lipophilic), the lipase reaction occurs at the interface between the aqueous and the oil phases. Hence, interfaces are the key spots for lipase biocatalysis and an appropriate site for modulating lipolysis. Surprisingly enough, knowledge about the effects of the interfacial composition on lipase catalysis is still limited and only described as "interfacial quality". By using a biophysical approach, a systematic study on the effects of the interfacial microenvironment on lipase catalysis is here made. The results demonstrate that inactivation of the lipase, as a function of interfacial composition, should be attributed to substrate inaccessibility and not to enzyme denaturation as previously hypothesized. Moreover, a detailed analysis of the interfacial properties of each molecule involved in triglyceride digestion revealed that lipolysis is a self-regulated process. The feedback mechanism can be explored as a new avenue to control lipase catalysis. To prove our point, we appreciably reduced triglyceride oil hydrolysis in a model gastro-intestinal system by interfacial engineering. We anticipate that our findings might provide a new approach for the understanding of lipase reactions at interfaces with direct applications to the biotechnology and health fields.