Porcelli M, Cacciapuoti G, Fusco S, Iacomino G, Gambacorta A, De Rosa M, Zappia V
Institute of Biochemistry of Macromolecules, Medical School, Second University of Naples, Italy.
Biochim Biophys Acta. 1993 Jul 10;1164(2):179-88. doi: 10.1016/0167-4838(93)90246-n.
S-Adenosylhomocysteine hydrolase from Sulfolobus solfataricus, a thermoacidophilic archaeon optimally growing at 87 degrees C, has been purified to homogeneity. The specific activity of the homogeneous enzyme is 161 nmol of S-adenosylhomocysteine formed per min per mg of protein, and the overall yield, by immunoaffinity purification, is 51%. The enzyme has a molecular mass of 190 kDa, is composed of four identical subunits (subunit mass 47 kDa), and contains four molecules of tightly-bound NAD+ per tetramer of which about 40% is in the reduced form. Physico-chemical features, including amino-acid composition and secondary structure, are reported. The pure protein, used to raise specific rabbit antisera, shows immunological properties different from other S-adenosylhomocysteine-metabolizing enzymes. The enzyme is thermophilic with an optimum temperature of 75 degrees C, and shows an apparent melting temperature of 95 degrees C by measuring its residual activity after 10 min incubation at increasing temperatures.
