SUMMARY: Nocardia salmonicolor, grown on acetate, commercial d,l-lactate or hydrocarbon substrates, has high isocitrate lyase activities compared with those resulting from growth on other carbon sources. This presumably reflects the anaplerotic role of the glyoxylate cycle during growth on the former substrates. Amongst a variety of compounds tested, including glucose, pyruvate and tricarboxylic acid cycle intermediates, only succinate and fumarate prevented an increase in enzyme activity in the presence of acetate. When acetate (equimolar to the initial sugar concentration) was added to cultures growing on glucose, there followed de novo synthesis of isocitrate lyase and isocitrate dehydrogenase, with increases in growth rate and glucose utilization, and both acetate and glucose were metabolized simultaneously. A minute amount of acetate (40 μm) caused isocitrate lyase synthesis (a three-fold increase in activity within 3 min of addition) when added to glucose-limited continuous cultures, but even large amounts added to nitrogen-limited batch cultures were ineffective. Malonate, at a concentration that was not totally growth-inhibitory (1 mm) prevented the inhibition of acetate-stimulated isocitrate lyase synthesis by succinate, but fumarate still inhibited in the presence of malonate. Phosphoenolpyruvate is a noncompetitive inhibitor of the enzyme (apparent Ki 1·7 mm).
The results are consistent with the induction of isocitrate lyase synthesis by acetate or a closely related metabolite, and catabolite repression by a C-4 acid of the tricarboxylic acid cycle, possibly fumarate.
AshworthJ. M.,
KornbergH. L.1963; Fine control of the glyoxylate cycle by allosteric inhibition of isocitrate lyase. Biochimica et biophysica acta 73:519–522
BeeverR. E.1975; Regulation of 2-phosphoenolpyruvate carboxykinase and isocitrate lyase in Neurospora crassa. Journal of General Microbiology 86:197–200
BennettP. M.,
HolmsW. H.1975; Reversible inactivation of the isocitrate dehydrogenase of Escherichia coliml308 during growth on acetate. Journal of General Microbiology 87:37–51
CooperR. A.,
KornbergH. L.1967; The direct synthesis of phosphoenolpyruvate from pyruvate by Escherichia coli. Proceedings of the Royal Society B 168:263–280
DavisJ. B.,
RaymondR. L.1961; Oxidation of alkyl-substituted cyclic hydrocarbons by a Nocardia during growth on n-alkanes. Applied Microbiology 9:383–388
FlavellR. B.,
WoodwardD. O.1971; Metabolic role, regulation of synthesis, cellular localization, and genetic control of the glyoxylate cycle enzymes in Neurospora crassa. Journal of Bacteriology 105:200–210
HermanN. J.,
BellE. J.1970; Metabolic control in Acinetobacter sp. I. Effect of C4 versus C2 and C3substrates on isocitrate lyase synthesis. Canadian Journal of Microbiology 16:769–774
HigginsI. J.,
SariaslaniF. S.1973; Control of isocitrate lyase in Nocardia salmonicolor (N.C.I.B. 9701). Proceedings of the Society for General Microbiology121
HildebrandtW.,
WeideH.1974; Isocitratlyase von Candida guilliermondii, Stamm H17. II. Regelung durch ausgewählte Intermediate des Tricarbonsäurezyklus und Hexoseabbaus. Zeitschrift für allgemeine Mikrobiologie 14:39–46
LowryO. H.,
RosebroughN. J.,
FarrA. L.,
RandallR. J.1951; Protein measurement with the Folin phenol reagent. Journal of Biological Chemistry 193:265–275
TrustT. J.,
MillisN. F.1970; The isolation and characterization of alkane-oxidizing organisms and the effect of growth substrate on isocitrate lyase. Journal of General Microbiology 61:245–254
WolfsonP. J.,
KrulwichT. A.1972; Inhibition of isocitrate lyase: the basis for inhibition of growth of two Arthrobacter species by pyruvate. Journal of Bacteriology 112:356–364