RT Journal Article SR Electronic(1) A1 Nguyen, Lieu Thi A1 Nguyen, Kien Trung A1 SpĂ­zek, Jaroslav A1 Behal, VladislavYR 1995 T1 The tylosin producer, Streptomyces fradiae, contains a second valine dehydrogenase JF Microbiology, VO 141 IS 5 SP 1139 OP 1145 DO https://doi.org/10.1099/13500872-141-5-1139 PB Microbiology Society, SN 1465-2080, AB SUMMARY 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 80000 and 41000, 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. , UL https://www.microbiologyresearch.org/content/journal/micro/10.1099/13500872-141-5-1139