STRUCTURAL FEATURES THAT GOVERN ENZYMATIC ACTIVITY IN
CARBONIC ANHYDRASE FROM A LOW TEMPERATURE ADAPTED FISH
CHIONODRACO HAMATUS
Stefano Marino 1, Kuniko Hayakawa 2, Keisuke Hatada 2, Maurizio Benfatto 2, Antonia Rizzello 3, Michele Maffia 3 and Luigi Bubacco 1*
1 University of Padova
2 Laboratori Nazionali di Frascati dell'INFN
3 University of Lecce,
* To whom correspondence should be addressed. E-mail: bubacco{at}mail.bio.unipd.it.
Submitted on February 23, 2007
Revised on March 26, 2007
Accepted on 5 June 2007
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Abstract |
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The carbonic anhydrase (CA1) family of zinc metalloenzymes includes many known isozymes which have different subcellular distributions. The study described here is focused on the identification of the structural features that define low temperature adaptation in a Chionodraco hamatus protein, both at an atomic level for the reaction center and for the tertiary structure of the protein. To this aim, a XANES/MXAN analysis of the reaction center was undertaken for both a structurally characterized human CAII (hCAII) and for CA of C. hamatus (Ice-CA). Higher structural levels were analyzed by sequence comparison and homology modeling. To stablish if the structural insights acquired in fish CAs are general, theoretical models were generated by homology modeling for three temperate climate-adapted fish CAs. The measured structural differences between the two proteins are discussed in terms of the differences in the electrostatic potential between hCAII and Ice-CA. We conclude that modulation of the interaction between the catalytic water molecule and the zinc ion could depend on the effect of the electrostatic potential distribution.
Key Words:
XANES, carbonic anhydrase, catalysis, electrostatic, metalloenzymes, zinc
