Microbiological Studies of Coli-aerogenes Bacteria

Part VIII. The Occurrence of Isocitritase and Citritase

Abstract

1) It was found with coli-aerogenes that two kinds of citrate-splitting enzymes, i.e. citritase and isocitritase, were formed when the organisms were grown on citrate.
2) The mode of degradation of citrate was suggested to be as follows:
[I] Citrate ^citritase→acetate+oxalacetate
Citrate^{TCA cycle}→succinate+4H+2C0₂
Oxalacetate+4H→succinate
Sum: 2 Citrate→2 succinate+acetate+2C0₂
[II] Citrate^cartas→acetate+ oxalacetate
Citrate ^isocitritase→glyoxylate+succinate
Oxalacetate→acetate+2H+2CO₂ Acetate+glyoxylate+2H→succinate
Sum: 2 Citrate→2 suceinate+acetate+2CO₂
3) The cell free extracts of both strains B-T and B-2 of coli-aerogenes were fractionated for isocitritase and citritase.
4) The yields of keto-acids obtained by the degradation of citrate were observed to vary from bacterial strain to a strain.
5) The presence of a large amount of suc-cinate brought about a striking inhibition on the action of isocitritase while no inhibiting ef-fect was observed on the action of citritase.
6) The action of either isocitritase or citritase was not influenced by the presence of antibiotics (dihydrostreptomycin, chloramphenicol and tet-racycline) and other inhibitors such as 2, 4 dinitrophenol, NaN₃, NaF, o-phenanthroline and αα'-dipyridyl.