Identification and Biochemical Characterization of a Thermostable Malate Dehydrogenase From the Mesophile Streptomyces Coelicolor A3(2)

Biosci Biotechnol Biochem. 2010;74(11):2194-201. doi: 10.1271/bbb.100357. Epub 2010 Nov 7.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Catalysis
  • Enzyme Inhibitors
  • Enzyme Stability
  • Hot Temperature*
  • Kinetics
  • Malate Dehydrogenase / metabolism*
  • Malates / metabolism
  • NAD
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
  • Streptomyces coelicolor / enzymology*

Substances

  • Enzyme Inhibitors
  • Malates
  • NAD
  • malic acid
  • Malate Dehydrogenase