J. Biochem, 1974, Vol. 76, No. 6 1327-1335
© 1974 Japanese Biochemical Society
research-article |
Some Properties of Metal Ion-independent Adenosine Triphosphatase from Dog Kidney
Tokyo Research Laboratories, Kowa Co., Ltd. Higashi-Murayama-shi, Tokyo 189
A new type of ATPase [EC 3.6.1.3 [EC] ], which is independent of metal ions, was previously purified from dog renal cortex. Using the highly purified enzyme (specific activity: 25 µmoles P1 released/mg protein·min), the effects of various reagents on the activity were studied. The molecular weight of the enzyme was estimated to be approximately 55,000.
- The activity was inhibited to 40% at pH 6.2 and 37° in the presence of 1 mM ascorbate. The ascorbate inhibition was neutralized by histidine, imidazole, arginine, or creatinine; these reagents somewhat stimulated the activity.
- The ascorbate inhibition was markedly increased in the presence of 10 µM Cu2+, which by itself did not affect the activity. This increased inhibition was also completely neutralized in the presence of histidine, imidazole, arginine, or creatinine.
- The activity was completely inhibited by 20 µM N-bromosuccinimide. This inhibition was also neutralized by histidine, imidazole, arginine, or creatinine.
- Enzyme activity previously inactivated by ascorbate was partially restored by adding histidine or arginine, but enzyme activity previously inactivated by N-bromosuccinimide was not restored.
- Neither histidine nor creatinine neutralized inhibition by ADP or ATP.
- Histidine and imidazole did not change the Km value of the enzyme for ATP, though they increased the Vmax value of the enzyme.