, 2011). For information on the commercial value and application of cold-active enzymes, Saracatinib we suggest reading Marx et al. (2007). One of the major adaptations of cold-proteins includes modifications of structural features that increase flexibility, and specific amino acids have emerged as key elements (Marx et al., 2007). Glycine has been reported as an important residue to improve the flexibility of protein structure, providing more amplitude to the relative movements between elements of the secondary structure. In pioneering work, Saunders et al. (2003) compared the global proteomes of two cold-adapted Archaea (Methanogenium frigidum

and Methanococcoides burtonii) with mesophilic proteomes. They found that these cold-adapted prokaryotes displayed higher frequencies of charged polar residues (mainly Gln and Thr) and a lower frequency of hydrophobic amino acids, mainly Leu. Using a different approach, find more Gianese et al. (2001) showed that, among psychrophilic enzymes, Ala and Asn were increased and Arg decreased at exposed sites, and some other differences

were found within α-helices and β-strands. More recently, Grzymski et al. (2006) showed that the most significant changes found in Antarctic bacterial protein sequences were a reduction of Pro, stabilizing hydrophobic clusters, and in salt-bridge-forming residues (Arg, Glu, and Asp). The availability of more genome sequences from psychrophilic microorganisms will be crucial

for understanding the adaptation of proteins to a cold environment, which in turn will have an obvious biotechnological application. Relevant biotechnological cold-active bacterial enzymes have been identified using culture-dependent studies (Margesin & Schinner, 1994; Vazquez et al., 2004; Martínez-Rosales & Castro-Sowinski, 2011; among many others). Currently, however, the most promising approach is based upon metagenomics, a culture-independent genomic Resveratrol analysis. Functional metagenomics relies on the extraction of environmental DNA and subsequent cloning to eventually identify the entire genetic set of a habitat. This allows the analysis of a wide diversity of genes and their products as well as the study of their potential for biotechnological use (Schmeisser et al., 2007). Through metagenomics, several cold-active enzymes with many potential biotechnological applications have been identified, cloned in heterologous hosts and characterized. Examples include lipases and esterases (Cieslinski et al., 2009; Heath et al., 2009; Yuhong et al., 2009; Berlemont et al., 2011; Yu et al., 2011; Hu et al., 2012), proteases (Berlemont et al., 2011; Zhang et al., 2011), cellulases (Berlemont et al., 2011), and glycosyl hydrolases (Berlemont et al., 2009, 2011).