Author:
Kim Hakryul,Mozaffar Zahid,Weete John D.
Abstract
Isocitrate dehydrogenase is considered to be one of the key regulatory enzymes in the conversion of glucose into fatty acids by oleaginous microorganisms. A dual coenzyme-specific isocitrate dehydrogenase (EC 1.1.1.41) (IDH) was isolated from the primitive fungus Pythium ultimum and purified by 211-fold by sequential ion-exchange, affinity, and gel filtration chromatographies. Specific activity of the partially purified enzyme was 76.2 μmol/(min∙mg protein) with NAD+and 40% less active with NADP+. Optimum pH for activity was 8.5–9.5. Kmvalues for threo-D-isocitrate and NAD+were 0.031 and 0.55 mM, respectively. The estimated molecular mass of the IDH was 96 kDa under nondenaturing conditions and 48 kDa under denaturing conditions, suggesting that the enzyme is composed of two subunits of the same size. The enzyme was relatively stable up to 55 °C, but no activity was detected after exposure to 65 °C for 15 min. Mg2+or Mn2+were required for activity.Key words: isocitric dehydrogenase, Pythium ultimum, dual cofactor specific, oleaginicity.
Publisher
Canadian Science Publishing
Subject
Genetics,Molecular Biology,Applied Microbiology and Biotechnology,General Medicine,Immunology,Microbiology
Cited by
2 articles.
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