Properties of silkworm Na⁺/K⁺-ATPase

• Published in: Journal of biochemistry (Tokyo) Vol. 148; no. 5; pp. 623 - 630
• Main Author: Homareda, Haruo
• Format: Journal Article
• Language: English
• Published: England Japanese Biochemical Society 01.11.2010; Oxford University Press
• Subjects: Animals; Bombyx - enzymology; Bombyx mori; Calcium Chloride - pharmacology; dog; Dogs; Hydrogen-Ion Concentration; K+-ATPase; Magnesium Chloride - pharmacology; Na+; nerve tissue; Nerve Tissue - enzymology; ouabain; Ouabain - pharmacology; Potassium - metabolism; silkworm; Sodium - metabolism; Sodium-Potassium-Exchanging ATPase - antagonists & inhibitors; Sodium-Potassium-Exchanging ATPase - metabolism; Temperature
• ISSN: 0021-924X; 1756-2651
• DOI: 10.1093/jb/mvq104

The high Na⁺ and low K⁺ concentrations in mammalian blood are maintained by Na⁺/K⁺-ATPase. In contrast, the K⁺ concentration is higher than the Na⁺ concentration in the hemolymph of the silkworm Bombyx mori, a Lepidopterous insect. Although Na⁺/K⁺-ATPase, therefore, appears not to be in silkworm, we confirmed the presence of Na⁺/K⁺-ATPase in nerve tissues of silkworm but not in skeletal muscle or the dorsal vessel. The enzymatic properties of silkworm Na⁺/K⁺-ATPase were characterized in detail and compared with those of dog Na⁺/K⁺-ATPase. Silkworm Na⁺/K⁺-ATPase had a much lower affinity for K⁺ and a somewhat higher affinity for Na⁺ than dog Na⁺/K⁺-ATPase. The optimal temperature of silkworm Na⁺/K⁺-ATPase activity was lower than that of dog Na⁺/K⁺-ATPase. The optimal Mg²⁺ concentration, pH and sensitivities to Ca²⁺ and ouabain, a specific inhibitor of Na⁺/K⁺-ATPase, of the two ATPases were identical. These results indicate that the enzymatic properties of the silkworm Na⁺/K⁺-ATPase are suitable for its growth, despite the differences between dog and silkworm Na⁺/K⁺-ATPases. Antisera raised against dog Na⁺/K⁺-ATPase recognized only the α-subunit of silkworm Na⁺/K⁺-ATPase.