Study on the Biosynthesis on Neomycin: Characterization of Isocitrate Dehydrogenase of the Neomycin Producer, Streptomyces fradiae and its Possible Relation to the Regulation of Biosynthesis of Neomycin

Study on the Biosynthesis on Neomycin: Characterization of Isocitrate Dehydrogenase of the Neomycin Producer, Streptomyces fradiae and its Possible Relation to the Regulation of Biosynthesis of Neomycin

S. fradiae showed very high activity of isocitrate dehydrogenase compared to other microorganisms. The activity of this enzyme was increased with the growth of the organism. But the increase might not imply its involvement in the growth. Rather its increased activity seemed to have a connection with the biosynthesis of neomycin. The enzyme showed high specificity toward $NADP^+$ and D-isocitrate with Km values of 5.75 and 6.74 uM, respectively, It was activated by $Mn^{2+}$. Its molecular weight was estimated from its gel retardation coefficient to be in the range of 61,000-63,000 daltons and its optimum pH was 8.0. The enzyme was thermally unstable.