Structural Features that Govern Enzymatic Activity in Carbonic Anhydrase from a Low-Temperature Adapted Fish, Chionodraco hamatus

Abstract

The carbonic anhydrase (CA) family of zinc metalloenzymes includes many known isozymes that have different subcellular distributions. The study described here focuses on identification of the structural features that define low-temperature adaptation in a Chionodraco hamatus protein, both for the reaction center, at an atomic level, and for the tertiary structure of the protein. To this aim, an x-ray absorption near-edge spectroscopy/Minuit x-ray absorption near-edge spectroscopy analysis of the reaction center was undertaken for both a structurally characterized human CAII and CA of C. hamatus. Higher structural levels were analyzed by sequence comparison and homology modeling. To establish whether 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 human CAII and CA of C. hamatus. 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.

Mapping Proton Wires in Proteins: Carbonic Anhydrase and GFP Chromophore Biosynthesis

“…The surface electrostatic potential density of CA-II can be seen in Figure 2B (top) of ref 44. Asp72 and Glu69 are located within a negative region on the rim of the "caldera" surrounding the active site.…”

Exploring Local Flexibility/Rigidity in Psychrophilic and Mesophilic Carbonic Anhydrases

“…Ice-CA consists of 259 residues with an acetylated N-terminus; it has been shown to have a shift of the optimal temperature toward low values, an increased catalytic rate, and relatively low activation energy (13). Because of its cytoplasmic localization, its high sensitivity to sulphonamides, and the analysis of the amino acids within 10 Å from the catalytic core, the cold-adapted Ice-CA isoform can be considered closely related to the mammalian CAII isoform (13)(14)(15). However, similarly to CAIII, Ice-CA is also S-glutathionylated, suggesting a protective action of S-glutathionylation against oxidative stress (13).…”

Tissue‐based transcriptomics of Chionodraco hamatus: Sequencing, de novo assembly, annotation and marker discovery

“…It was equally demonstrated that, despite the loss of haemoglobin, C. hamatus has developed a functional nitrous oxide system (NOS) which seems to be responsible for paracrine–autocrine regulatory functions (Pellegrino et al ., ). Studies on C. hamatus have proven that carbonic anhydrase (CA) activity can influence oxygen transport in this species (Marino et al ., ). At the immunological level, it has been also reported that the cytokine IL‐1β is an important molecule in the immune response of icefishes against gram‐negative bacteria (Buonocore et al ., ).…”

“…Studies on C. hamatus have proven that carbonic anhydrase (CA) activity can influence oxygen transport in this species (Marino et al, 2007). At the immunological level, it has been also reported that the cytokine IL-1β is an important molecule in the immune response of icefishes against gram-negative bacteria (Buonocore et al, 2006).…”