title: Two distinct arginine kinases in Neocaridina denticulate: psychrophilic and mesophilic enzymes.
abstract: The small shrimp Neocaridina denticulata has two types of arginine kinases (AKs): AK1 and AK2. We determined the full kinetic parameters for the forward reaction of the AKs at temperatures between 15 and 35°C. The catalytic efficiencies, determined by kcat/(Ka(ATP)·Kia(ARG)), of the two enzymes showed a marked difference in temperature dependence. The efficiency of AK2 decreased markedly with decreasing temperature, while that of AK1 did not decrease with decreasing temperature, suggesting that AK1 is a cold-adapted enzyme. This unusual characteristic of AK1 was attributable to the remarkable decrease in Kia(ARG) with decreasing temperature, which enlarges its catalytic efficiency. Criterion with the values of Δ(ΔH(o‡))p-m and Δ(TΔS(o‡))p-m also indicate that AK1 is a psychrophilic enzyme and AK2 is mesophilic.
authors.affiliation: Laboratory of Biochemistry, Faculty of Science, Kochi University, Kochi 780-8520, Japan. Electronic address: suzuki@kochi-u.ac.jp.
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Suzuki
authors.affiliation: Laboratory of Biochemistry, Faculty of Science, Kochi University, Kochi 780-8520, Japan.
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Kanou
mesh_terms: D000818:Animals; D001122:Arginine Kinase / Q000737:chemistry* / Q000302:isolation & purification; D003445:Crustacea / Q000201:enzymology*; D004795:Enzyme Stability; D007700:Kinetics; D013696:Temperature
chemical_list: D001122:Arginine Kinase
keywords: Arginine kinase; Guanidino kinase; Neocaridina denticulata; Phosphagen kinase; Psychrophilic enzyme