PSYCHROPHILIC ENZYMES - A THERMODYNAMIC CHALLENGE

Psychrophilic microorganisms, hosts of permanently cold habitats, prod uce enzymes which are adapted to work at low temperatures. When compar ed to their mesophilic counterparts, these enzymes display a higher ca talytic efficiency over a temperature range of roughly 0-30 degrees C and a high thermosensitivity. The molecular characteristics of cold en zymes originating from Antarctic bacteria have been approached through protein modelling and X-ray crystallography. The deduced three-dimens ional structures of cold alpha-amylase, beta-lactamase, lipase and sub tilisin have been compared to their mesophilic homologs. It appears th at the molecular adaptation resides in a weakening of the intramolecul ar interactions, and in some cases in an increase of the interaction w ith the solvent, leading to more flexible molecular edifices capable o f performing catalysis at a lower energy cost. (C) 1997 Elsevier Scien ce B.V.