AbstractEnzymes adapted to cold display structures comparable with those of their meso‐ and thermophilic homologs but are characterized by a higher catalytic efficiency at low temperatures and by thermolability at moderate temperatures. To identify the structural factors responsible of such features, we undertook a systematic comparative analysis of several structural properties in a data set consisting of 7 cold active enzymes belonging to different structural families and 28 related structures from meso/thermophiles representing most of the structural information now available. Only high‐resolution and high‐quality structures were considered. Properties were calculated and then compared for each pair of 3D structures displaying different temperatures of adaptation using a temperature‐weighting scheme. The significance of the resulting differences was evaluated with a statistical method. Results reveal that each protein family adopts different structural strategies to adapt to low temperatures. However, some common trends are observed: the number of ion pairs, the side‐chain contribution to the exposed surface, and the apolar fraction of the buried surface show a consistent decrease with decreasing optimal temperatures. Proteins 2002;47:236–249. © 2002 Wiley‐Liss, Inc.