کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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1975410 | 1060624 | 2013 | 9 صفحه PDF | دانلود رایگان |
A functional urea cycle with both cytosolic (ARG I) and mitochondrial (ARG II) arginase activity is present in the liver of an ureogenic air-breathing teleost, Heteropneustes fossilis. Antibodies against mammalian ARG II showed no cross-reactivity with the H. fossilis ARG II. ARG II was purified to homogeneity from H. fossilis liver. Purified ARG II showed a native molecular mass of 96 kDa. SDS–PAGE showed a major band at 48 kDa. The native enzyme, therefore, appears to be a homodimer. The pI value of the enzyme was 7.5. The purified enzyme showed maximum activity at pH 10.5 and 55 °C. The Km of purified ARG II for l-arginine was 5.25 ± 1.12 mM. l-Ornithine and Nω-hydroxy-l-arginine showed mixed inhibition with Ki values 2.16 ± 0.08 and 0.02 ± 0.004 mM respectively. Mn+ 2 and Co+ 2 were effective activators of arginase activity. Antibody raised against purified H. fossilis ARG II did not cross-react with fish ARG I, and mammalian ARG I and ARG II. Western blot with the antibodies against purified H. fossilis hepatic ARG II showed cross reactivity with a 96 kDa band on native PAGE and a 48 kDa band on SDS–PAGE. The molecular, immunological and kinetic properties suggest uniqueness of the hepatic mitochondrial ARG II in H. fossilis.
Journal: Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology - Volume 164, Issue 2, February 2013, Pages 133–141