{'fraction_non_alphanumeric': 0.02247191011235955, 'fraction_numerical': 0.0028089887640449437, 'mean_word_length': 5.720754716981132, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Temperature: a "shaping force' in protein evolution.

1. Comparisons of homologous enzymes from species adapted to widely different temperatures reveal that ligand-binding affinities are rigorously conserved. This is interpreted to mean that a critical relationship between ligand-binding ability and intracellular ligand concentrations must be maintained for proper enzymic regulation. 2. The catalytic efficiencies of enzyme homologues differ in temperature-compensatory manners. Activation free energies are proportional to adaptation temperature and, consequently, low-temperature-adapted enzymes have the highest substrate turnover numbers. 3. Temperature compensatory adjustments in catalytic efficiency may be achieved by altering the number of weak bonds that form or break during a catalytic conformational change. Support for this hypothesis comes from the finding that activation enthalpy and activation entropy values co-vary in a regular manner and by magnitudes consistent with different amounts of weak-bond formation/rupture during catalytic activation in differnt enzyme homologues. 4. Adaptive adjustments in ligand-binding energetics may also involve utilization of the energy changes that occur during conformational changes. This mechanism would permit enzymes with identical binding-site chemistries to display adaptively different ligand affinities. 5. The greater heat-stabilities of enzymes from warm-adapted species may cause these enzymes to be less efficient catalysts than cold-adapted heat-labile enzymes. Heat-stable enzymes may have to break more weak bonds during a catalytic conformational change than do cold-adapted enzymes. The requirements for thermal stability and high catalytic efficiency thus appear to force an adaptational 'compromise'.