title: The tylosin producer, Streptomyces fradiae, contains a second valine dehydrogenase.
abstract: A second NAD-dependent valine dehydrogenase (VDH) of Streptomyces fradiae was detected and purified to homogeneity by affinity chromatography on Reactive-Blue 2 Sepharose followed by gel filtration and Mono Q fast protein liquid chromatography. The relative molecular masses of the native enzyme and its subunits were determined to be 80,000 and 41,000, respectively, indicating that the enzyme is a homodimer. The enzyme was the only active VDH in S. fradiae; its activity was significantly induced by L-valine, but was repressed by ammonia. Among branched- and straight-chain amino acids that serve as enzyme substrates, L-2-aminobutyrate and L-valine are preferred. Significant activities were found with deamino-NAD+ and 3-pyridinealdehyde-NAD+. The molecular and catalytic properties of the enzyme distinguish it from the enzyme previously purified, and thus indirectly indicate the existence of two VDHs in S. fradiae.
authors.affiliation: Institute of Microbiology, Academy of Sciences of the Czech Republic, Víde:ntskà 1083, 142 20 Prague 4,Czech Republic.
authors.forename: Lieu Thi
authors.initials: LT
authors.lastname: Nguyen
authors.affiliation: Institute of Microbiology, Academy of Sciences of the Czech Republic, Víde:ntskà 1083, 142 20 Prague 4,Czech Republic.
authors.forename: Kien Trung
authors.initials: KT
authors.lastname: Nguyen
authors.affiliation: Institute of Microbiology, Academy of Sciences of the Czech Republic, Víde:ntskà 1083, 142 20 Prague 4,Czech Republic.
authors.forename: Jaroslav
authors.initials: J
authors.lastname: Spízek
authors.affiliation: Institute of Microbiology, Academy of Sciences of the Czech Republic, Víde:ntskà 1083, 142 20 Prague 4,Czech Republic.
authors.forename: Vladislav
authors.initials: V
authors.lastname: Behal
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D004591:Electrophoresis, Polyacrylamide Gel; D007527:Isoenzymes / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D046911:Macromolecular Substances; D008970:Molecular Weight; D013045:Species Specificity; D013302:Streptomyces / Q000201:enzymology*; D013379:Substrate Specificity; D015645:Tylosin / Q000096:biosynthesis*; D050802:Valine Dehydrogenase (NADP+)
chemical_list: D007527:Isoenzymes; D046911:Macromolecular Substances; D000594:Amino Acid Oxidoreductases; D050802:Valine Dehydrogenase (NADP+); D015645:Tylosin