Identification and biochemical characterization of a thermostable malate dehydrogenase from the mesophile Streptomyces coelicolor A3(2).
We identified and characterized a malate dehydrogenase from Streptomyces coelicolor A3(2) (ScMDH). The molecular mass of ScMDH was 73,353.5 Da with two 36,675.0 Da subunits as analyzed by matrix-assisted laser-desorption ionization-time-of-flight mass spectrometry (MALDI-TOF-MS). The detailed kinetic parameters of recombinant ScMDH are reported here. Heat inactivation studies showed that ScMDH was more thermostable than most MDHs from other organisms, except for a few extremely thermophile bacteria. Recombinant ScMDH was highly NAD(+)-specific and displayed about 400-fold (k(cat)) and 1,050-fold (k(cat)/K(m)) preferences for oxaloacetate reduction over malate oxidation. Substrate inhibition studies showed that ScMDH activity was inhibited by excess oxaloacetate (K(i)=5.8 mM) and excess L-malate (K(i)=12.8 mM). Moreover, ScMDH activity was not affected by most metal ions, but was strongly inhibited by Fe(2+) and Zn(2+). Taken together, our findings indicate that ScMDH is significantly thermostable and presents a remarkably high catalytic efficiency for malate synthesis.
Key Laboratory of Molecular Evolution and Biodiversity and Institute of Molecular Biology and Biotechnology, and Key Laboratory of the Biotic Environment and Ecological Safety in Anhui Province, Anhui Normal University, Wuhu, China.
Ya-Dong
YD
Ge
Zheng-Yu
ZY
Cao
Zong-Da
ZD
Wang
Lu-Lu
LL
Chen
You-Ming
YM
Zhu
Guo-Ping
GP
Zhu
D002384:Catalysis; D004791:Enzyme Inhibitors; D004795:Enzyme Stability; D006358:Hot Temperature; D007700:Kinetics; D008291:Malate Dehydrogenase / Q000378:metabolism*; D008293:Malates / Q000378:metabolism; D009243:NAD; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D048372:Streptomyces coelicolor / Q000201:enzymology*
D004791:Enzyme Inhibitors; D008293:Malates; D009243:NAD; C030298:malic acid; D008291:Malate Dehydrogenase