Chapter 5 - Molecular mechanisms behind the cold and hot adaptation in extremozymes

Abstract

Extremozymes are enzymes derived from extremophiles mainly archea and bacteria and are well know for thier biocatalytic potential in various industries. Extremophiles may endure and flourish in harsh environmental conditions such as hot springs, deep sea vents, geysers, geothermal volcanic areas, and glaciers. Psychrophilic microbes are the soucre of many cold-adapted enzymes whereas thermophiles and hyperthermophiles are the producer of hot-adapted enzymes. Psychrophilic enzymes show elevated catalytic activity at low temperature and required due to their inherent flexible structure. While thermophilic enzymes performs well in extreme hot due to their excellent thermo and kinetic stability. These adaptations also depend on alteration in the amino acid sequence, structural modifications, flexibility, charge and/or hydrophobicity of the proteins. In psychrophiles, structural features that are responsible for the cold adaptations include production of cold-shock proteins, decreased number of salt bridges, less arginine/lysine ratio with increased number of glycine in the loop and lesser number of proline, and antifreeze proteins required for inhibition of ice crystal in growth. On the other hand, hot-adapted enzymes exhibit shorter loops, thereby inhibiting non-specific interactions that in turn induces flexibility at high temperatures. Apart from these, tight hydrophobic core packing, increased number of disulfide bond, which ameliorates their structural rigidity and resists unfolding at high temperatures are also involved in hot adaptaion. Only those enzymes that fulfill these molecular adapations are considered to be useful in industrial applications including agriculture, food, feed, beverage, pharmaceutical, detergent, leather, pulp, leather etc. This book chapter primarily explores the adaptive molecular mechanisms of an enzyme 1 that facilitate the hot and cold adaption.