Comparison and Characterization of Arginine Kinases Purified from the PrawnPenaeus japonicus(Kurumaebi) and the Swimming CrabPortunus trituberculatus(Gazami)

Abstract

The physico-chemical characteristics of purified arginine kinases from prawn and swimming crab were examined. The molecular weights of prawn and swimming crab enzymes were 40,500 and 40,000, respectively. Amino acid analysis indicated that there were some differences in the contents of proline, glycine, methionine, and lysine. The other amino acid compositions of these enzymes resembled each other.Both enzymes were stable up to 20°C when they were treated for 10 min at various temperature levels. The enzymes lost their activities at temperatures higher than 25°C. They were more stable at pH 8.0 than pH 7.0. The optimum temperature for the enzyme of prawn was about 4rC and that for swimming crab was about 40°C. The pH optima for the activity of arginine kinase of prawn in the forward and in the reverse reactions were found to be 9.0 and 6.1, respectively. For the swimming crab, the similar optimum pHs at 9.2 in the forward reaction and 5.8 in the reverse reaction were observed. Both enzymes were activated most strongly with Mg2 + and Mn 2 + followed by Ca 2 + , Co 2 + , and Fe 2 + • The enzymes were not activated by Sr2 +, Cu 2 +, or Zn 2 + •The optimum molar ratio of Mg2 +: A TP in the forward reaction of prawn and swimming crab was found to be 1 : 1, and the molar ratio of Mg2 +: ADP in the reverse reaction was 4: 1 in both cases. Kinetic studies indicated that dissociation constants were rather different. In the prawn, dissociation constants for arginine, ATP, AP, and ADP were 0.19, 0.31, 0.67, al)d 0.29mM, respectively, but in the swimming crab, they were 0.10, 0.18, 0.22, and 0.11 mM, respectively.