title: Pyridine dinucleotide biosynthesis in archaebacteria: presence of NMN adenylyltransferase in Sulfolobus solfataricus.
abstract: The enzyme NMN adenylyltransferase, leading to NAD synthesis, has been observed for the first time in soluble extracts from the extreme acidothermophilic archaeon Sulfolobus solfataricus. Comparison of its molecular and kinetic properties with those of the enzyme isolated from prokaryotes and eukaryotes revealed significant differences, knowledge of which may contribute to the understanding of metabolic evolutionary mechanisms. The thermophilic enzyme shows a molecular mass of about 66,000 and an isoelectric point of 5.4. The Km values for ATP, NMN and nicotinic acid mononucleotide are 0.08 microM, 1.4 microM and 17 microM, respectively. The enzyme shows a remarkable degree of thermophilicity, with an activation energy of 95 kJ/mol.
authors.affiliation: Istituto di Biochimica, Facoltà di Medicina e Chirurgia, Università di Ancona, Italy.
authors.forename: N
authors.initials: N
authors.lastname: Raffaelli
authors.forename: A
authors.initials: A
authors.lastname: Amici
authors.forename: M
authors.initials: M
authors.lastname: Emanuelli
authors.forename: S
authors.initials: S
authors.lastname: Ruggieri
authors.forename: G
authors.initials: G
authors.lastname: Magni
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D006358:Hot Temperature; D007526:Isoelectric Point; D007700:Kinetics; D008970:Molecular Weight; D009243:NAD / Q000096:biosynthesis*; D009537:Nicotinamide Mononucleotide / Q000378:metabolism; D009612:Nicotinamide-Nucleotide Adenylyltransferase / Q000302:isolation & purification / Q000378:metabolism*; D013347:Subcellular Fractions / Q000201:enzymology; D016944:Sulfolobus / Q000201:enzymology*
chemical_list: D009243:NAD; D009537:Nicotinamide Mononucleotide; D000255:Adenosine Triphosphate; D009612:Nicotinamide-Nucleotide Adenylyltransferase