Structural insights into cold inactivation of tryptophanase and cold adaptation of subtilisin S41

• Published in: Biopolymers Vol. 89; no. 5; pp. 354 - 359
• Main Authors: Almog, Orna, Kogan, Anna, Leeuw, Marina de, Gdalevsky, Garik Y., Cohen-Luria, Rivka, Parola, Abraham H.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.05.2008
• Subjects: Adaptation, Physiological; Cold Temperature; crystal structure; Enzyme Activation - physiology; Enzyme Stability - physiology; hydrophobic interactions; Models, Molecular; PLP-dependent enzymes; Protein Conformation; psychro-meso-and thermophilic organisms; quaternary structure; Subtilisin - physiology; surface charge; Temperature; thermolabile; Tryptophanase - physiology
• ISSN: 0006-3525; 1097-0282
• DOI: 10.1002/bip.20866

A wide variety of enzymes can undergo a reversible loss of activity at low temperature, a process that is termed cold inactivation. This phenomenon is found in oligomeric enzymes such as tryptophanase (Trpase) and other pyridoxal phosphate dependent enzymes. On the other hand, cold‐adapted, or psychrophilic enzymes, isolated from organisms able to thrive in permanently cold environments, have optimal activity at low temperature, which is associated with low thermal stability. Since cold inactivation may be considered “contradictory” to cold adaptation, we have looked into the amino acid sequences and the crystal structures of two families of enzymes, subtilisin and tryptophanase. Two cold adapted subtilisins, S41 and subtilisin‐like protease from Vibrio, were compared to a mesophilic and a thermophilic subtilisins, as well as to four PLP‐dependent enzymes in order to understand the specific surface residues, specific interactions, or any other molecular features that may be responsible for the differences in their tolerance to cold temperatures. The comparison between the psychrophilic and the mesophilic subtilisins revealed that the cold adapted subtilisins have a high content of acidic residues mainly found on their surface, making it charged. The analysis of the Trpases showed that they have a high content of hydrophobic residues on their surface. Thus, we suggest that the negatively charged residues on the surface of the subtilisins may be responsible for their cold adaptation, whereas the hydrophobic residues on the surface of monomeric Trpase molecules are responsible for the tetrameric assembly, and may account for their cold inactivation and dissociation. © 2007 Wiley Periodicals, Inc. Biopolymers 89: 354–359, 2008. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com