The tylosin producer, Streptomyces fradiae, contains a second valine dehydrogenase.
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.
Nguyen
Lieu Thi
LT
Institute of Microbiology, Academy of Sciences of the Czech Republic, Víde:ntskà 1083, 142 20 Prague 4,Czech Republic.
Nguyen
Kien Trung
KT
Institute of Microbiology, Academy of Sciences of the Czech Republic, Víde:ntskà 1083, 142 20 Prague 4,Czech Republic.
Spízek
Jaroslav
J
Institute of Microbiology, Academy of Sciences of the Czech Republic, Víde:ntskà 1083, 142 20 Prague 4,Czech Republic.
Behal
Vladislav
V
Institute of Microbiology, Academy of Sciences of the Czech Republic, Víde:ntskà 1083, 142 20 Prague 4,Czech Republic.
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+)
D007527:Isoenzymes; D046911:Macromolecular Substances; D000594:Amino Acid Oxidoreductases; D050802:Valine Dehydrogenase (NADP+); D015645:Tylosin