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Characterization of the arginine kinase from Desulfotalea psychrophila LSv54 : The effects of environmental conditions and catalytic domain sequence variations on enzymatic turnover
Author(s) -
Lockhart Chad,
Fraga Dean
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a299-b
Subject(s) - arginine kinase , biochemistry , arginine , enzyme , kinase , chemistry , pyruvate kinase , amino acid , biology , glycolysis
Arginine kinase (AK) catalyzes the transfer of a high‐energy phosphoryl group between ATP and arginine in invertebrates and protozoa. While AK has not been described in bacteria, we recently identified an arginine kinase gene in Desulfotalea psychrophila LSv54 (AKds) , a psychrophilic bacterium found in Arctic marine sediments. This protein was confirmed to be an arginine kinase and analysis of kinetic data indicated that while enzyme‐substrate binding affinities are very tight, levels of product turnover are significantly less than other phosphagen kinases. We hypothesize that arginine kinase's activity as a free energy regulator may contribute to the organism's ability to act as a sulfate reducer, playing an integral role in the carbon and sulfur cycles in marine sediments through the process of remineralization. A previous study of sulfate reduction in Desulfovibrio desulfuricans suggests ATP‐dependent activation of sulfate as the initial step in the sulfate reduction reaction (Peck, H. D. (1959) Biochem . 45 , –708). This study will compare the activity of the Desulfotalea AK to the AK of more temperate organisms under a variety of conditions acidic pH, high salt concentrations, and low temperatures to determine the relationship between the organism's optimal living conditions and the conditions for optimal AK activity. Studies on the possible residues that could influence turnover rate revealed a unique amino acid sequence variation within one catalytic domain. Through the use of site‐directed mutagenesis and subsequent kinetic analysis, the effects of this difference on enzymatic activity may be revealed.