Msm. Jetten et al., REGULATION OF PHOSPHO(ENOL)-PYRUVATE AND OXALOACETATE-CONVERTING ENZYMES IN CORYNEBACTERIUM-GLUTAMICUM, Applied microbiology and biotechnology, 41(1), 1994, pp. 47-52
The presence and properties of the enzymes involved in the synthesis a
nd conversion of phospho(enol)pyruvate (PEP) and oxaloacetate (OAA), t
he precursors for aspartate-derived amino acids, were investigated in
three different Corynebacterium strains. This study revealed the prese
nce of both PEP carboxykinase 0.29 mu mol.min(-1).mg(-1) of protein [u
nits (U) mg(-1))] and PEP synthetase (0.13 U.mg(-1)) in C. glutamicum
as well as pyruvate kinase (1.4 U.mg(-1)) and PEP carboxylase (0.16 U.
mg(-1)). With the exception of PEP carboxykinase these activities were
also present in glucose-grown C. flavum and C. lactofermentum Pyruvat
e carboxylase activity was not de tected in all three species cultivat
ed on glucose or lactate. At least five enzyme activities that utilize
OAA as a substrate were detected in crude extracts of C. glutamicum:
citrate synthase (2 U.mg(-1)), malate dehydrogenase (2.5 U.mg(-1)), gl
utamate:OAA transaminase (1 U.mg(-1)), OAA-decarboxylating activity (0
.89 U.mg(-1)) and the previously mentioned PEP carboxykinase (0.29 U.m
g(-1)). The partially purified OAA-decarboxylase activity of C. glutam
icum was completely dependent on the presence of inosine diphosphate a
nd Mn2+, had a Michaelis constant (K-m) of 2.0 mM for OAA and was inhi
bited by ADP and coenzyme A (CoA). Examination of the kinetic properti
es showed that adenine nucleotides and CoA derivatives have reciprocal
but reinforcing effects on the enzymes catalyzing the interconversion
of pyruvate, PEP and OAA in C. glutamicum. A model for the regulation
of the carbon flow based on these findings is presented.