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........ published in NEWSLETTER # 59

by Professor X. Malcata, Escola Superior de Biotecnologia, Porto (Portugal)

This book (NATO ASI SERIES E317) attempts to (i) systematically review the state-of-the-art pertaining to knowledge on the various levels of structure and catalytic function of lipases, and (ii) discuss in a simultaneously pragmatic and integrated manner the design and modification of lipases and the technological aspects of the utilization of lipases for desired practical purposes, in attempts to address four major issues, viz.:

1. NEED: Although several applications of lipases have been developed throughout the past two decades, innovative uses of these enzymes for a wide variety of organic syntheses and modification of existing fats and oils have increased exponentially during the last five years. A reason which may partly account for this trend is the increasing availability of lipases from (genetically engineered) microbial sources coupled with their special capacity to act as catalysts at hydrophilic/hydrophobic interfaces. As a result of the structural characterisation effected during the same period, applications of lipases can now be developed in a much more rational fashion; however, this purpose will not be fully achieved unless careful attempts to comprehensively clarify and integrate such advances are developed.

2. IMPORTANCE: Once viewed as solutions in search of problems, lipases have conquered a special position in the field of biotechnology since the advent of enzyme-catalyzed reactions in microaqueous media. This was a consequence of the fact that lipases are characterized by the unique feature that their active site is protected by a hydrophobic turn of the peptide sequence in the form of a lid which can be lifted (thus giving rise to full catalytic action) upon the presence of a hydrophilic/hydrophobic interface in the microenvironment of the enzyme. This feature makes these enzymes particularly useful for oleochemical production and transformation through hydrolysis/esterification since most of the products in question are partially (or totally) insoluble in water.

3. TIMELINESS: Knowledge about lipases has recently undergone a major boost through the successful structural and functional characterisation of ten lipases of microbial and mammalian origin sponsored by the EC-funded T-project on lipases within the framework of BRIDGE. This paneuropean project has led to the understanding of why and how such enzymes transform their natural substrates (especially when they are located at interfaces) through (i) cloning, expression, sequencing, isolation, and purification to a high level, (ii) characterisation of the catalytic mechanism, and (iii) crystallization and three- dimensional structure determination of these lipases.

4. USEFULNESS: Synergisms are expected from interchange of experiences between crystallographers, biochemists, geneticists, and enzyme kineticists, and food, chemical, and biochemical engineers. Hence, potential readers of the former group are likely to learn what the practical aims and constraints associated with industrial applications of lipases are (and thus be able to design lipases to meet these specifications), whereas potential readers of the latter group may learn how advantage can be had from the structural knowledge of lipases and their metabolic genesis to better design media, processes and products in terms of biochemical and technical feasibility (and to concomitantly optimize them in terms of volumetric efficiency).

This book thus addresses (i) the design and production of lipases with desired, pre-selected properties (i.e. engineering of lipases, which is strongly based on the knowledge of their primary, secondary, and tertiary structures), and (ii) the utilization of lipases for desired applied purposes (i.e. engineering with lipases, which is strongly based on knowledge of their mechanism of action and selectivity, as well as knowledge of bioreactor operation).
Reference books: A116, A178, A266, C100, C178, E317, H90

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