An ecto-enzyme from Sulfolobus acidocaldarius strain 7 which catalyzes hydrolysis of inorganic pyrophosphate, ATP, and ADP: purification and characterization.
Membranes of Sulfolobus acidocaldarius, a thermoacidophilic archaebacterium, show novel enzymatic activities to hydrolyze PPi, ATP, and ADP at an optimal pH of 3, equal to the growth optimum. The activity increased by about 2-fold on addition of PPi and/or Pi to the growth medium, when yeast extract and casamino acids were removed. The enzyme which hydrolyzes PPi at pH 3 was solubilized and purified by successive chromatographies. The final preparation showed a 26 kDa single band on SDS-PAGE, and a molecular mass of 35 kDa on gel permeation chromatography. The Km and Vmax for PPi were 0.16 mM and 33 mumol Pi released/min/mg at 55 degrees C. ATP and ADP were also good substrates. Divalent cations were not essential for activity. Substrate inhibition at more than 5 mM PPi, ATP or ADP was observed. AMP, glucose-6-phosphate, and p-nitrophenyl phosphate were not hydrolyzed at all. The activity was 4-fold stimulated by addition of the lipid fraction extracted from the organism.
Amano
T
T
Department of Life Science and Bioengineering, Tokyo Institute of Technology, Yokohama.
Wakagi
T
T
Oshima
T
T
D000244:Adenosine Diphosphate / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D002384:Catalysis; D003470:Culture Media; D011756:Diphosphates / Q000378:metabolism*; D004790:Enzyme Induction / Q000502:physiology; D006868:Hydrolysis; D011755:Pyrophosphatases / Q000096:biosynthesis / Q000737:chemistry / Q000302:isolation & purification*; D016945:Sulfolobus acidocaldarius / Q000201:enzymology*
D003470:Culture Media; D011756:Diphosphates; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D011755:Pyrophosphatases