Cold-adapted Features of Arginine Kinase from the Deep-sea Clam Calyptogena kaikoi

Abstract

The heterodont clam Calyptogena kaikoi, which inhabits depths exceeding 3,500 m where low ambient temperatures prevail, has an unusual two-domain arginine kinase (AK) with molecular mass of 80 kDa, twice that of typical AKs. The purpose of this work is to investigate the nature of the adaptations of this AK for functioning at low temperatures. Recombinant C. kaikoi AK constructs were expressed, and their two-substrate kinetic constants (k(cat), K(a), and K(ia)) were determined at 10°C and 25°C, respectively. When measured at 25°C, the K(ia) values were tenfold larger than those for corresponding K(a) values, while at 10°C, the K(ia) values decreased remarkably, but the K (a) values were almost unchanged. The Calyptogena two-domain enzyme has threefold higher catalytic efficiency, calculated by k (cat)/(K(a)(ARG)·K(ia)(ATP) ), at 10°C, than that at 25°C, reflecting adaptation for function at reduced ambient temperatures. The activation energy (E(a)) and thermodynamic parameters were determined for Calyptogena two-domain enzyme and compared with those of two-domain enzymes from mesophilic Corbicula and Anthopleura. The value for E(a) of Calyptogena enzyme were about half of those for mesophilic enzymes, and a larger decrease in entropy was observed in Calyptogena AK reaction. Although large decrease in entropy increases the ΔG(o‡) value and consequently lowers the k(cat) value, this is compensated with its lower E(a) value thereby minimizing the reduction in its k(cat) value. These thermodynamic properties, together with the kinetic ones, are also present in the separated domain 2 of the Calyptogena two-domain enzyme.

Rapid Statistical Optimization of Cultural Conditions for Mass Production of Carboxymethylcellulase by a Newly Isolated Marine Bacterium, Bacillus velezensis A-68 from Rice Hulls

“…Hyperthermophilic bacteria isolated from marine sediments and seawater can utilize glucans as well as hemicellulose such as xylans and mannans [1]. Cold-adapted amylase and arginine kinase were produced by marine bacteria [23,30].…”

Comparative proteomic analysis of cold seep clam Archivesica marissinica and shallow water shellfish Ruditapes philippinarum provides insights into the adaptation mechanisms of deep-sea mollusks

“…It facilitates the reversible exchange of the gamma-phosphoryl group between ATP and arginine, resulting in the production of ADP, phosphorylated guanidine, and energy (Uda et al, 2006). Researchers found that the catalytic efficiency of arginine kinases with two domains, derived from cold seep clams, exhibited a threefold increase at a temperature of 10 °when compared with that at to 25 ° (Suzuki et al, 2012). This finding suggests a potential mechanism by which cold seep shellfish can adapt to low-temperature surroundings.…”