In an effort to explore the role of glycine clusters on the cold adaptation of enzymes, we designed point mutations aiming to alter the distribution of glycine residues close to the active site of the psychrophilic alkaline phosphatase from the Antarctic strain TAB5. The mutagenesis targets were residues Gly261 and Gly262. The replacement of Gly262 by Ala resulted in an inactive enzyme. Substitution of Gly261 by Ala resulted to an enzyme with lower stability and increased energy of activation.