201. Unusual hepatic mitochondrial arginase in an Indian air-breathing teleost, Heteropneustes fossilis: purification and characterization.
- Author
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Srivastava S and Ratha BK
- Subjects
- Animals, Arginase isolation & purification, Arginine analogs & derivatives, Arginine metabolism, Biocatalysis drug effects, Blotting, Western, Cobalt pharmacology, Electrophoresis, Polyacrylamide Gel, Enzyme Activation drug effects, Fish Proteins isolation & purification, Hydrogen-Ion Concentration, India, Isoelectric Focusing, Kinetics, Manganese pharmacology, Molecular Weight, Ornithine metabolism, Substrate Specificity, Temperature, Arginase metabolism, Catfishes metabolism, Fish Proteins metabolism, Mitochondria, Liver enzymology
- Abstract
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 K(m) of purified ARG II for l-arginine was 5.25±1.12 mM. L-Ornithine and N(ω)-hydroxy-L-arginine showed mixed inhibition with K(i) 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., (Copyright © 2012 Elsevier Inc. All rights reserved.)
- Published
- 2013
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