C. Tricot et al., PURIFICATION AND PROPERTIES OF A SUCCINYLTRANSFERASE FROM PSEUDOMONAS-AERUGINOSA SPECIFIC FOR BOTH ARGININE AND ORNITHINE, European journal of biochemistry, 224(3), 1994, pp. 853-861
The arginine and ornithine succinyltransferase from Pseudomonas aerugi
nosa, a bifunctional enzyme involved in the aerobic utilization of arg
inine and ornithine, has been purified to homogeneity. The apparent mo
lecular mass of the native enzyme was 150 kDa by gel filtration and 14
0 kDa by polyacrylamide gel electrophoresis under non-denaturing condi
tions. After SDS/PAGE two subunits of 35 kDa and 37 kDa were evident,
indicating that the enzyme is a heterotetramer. Microsequence analysis
of the electroblotted protein bands gave two different but well-conse
rved N-terminal amino acid sequences. The L-arginine saturation curve
followed Henri-Michaelis kinetics with an apparent K, value of 0.5 mM.
The sigmoidal saturation curve for L-ornithine indicated allosteric b
ehaviour. D-Arginine, a competitive inhibitor with respect to L-argini
ne, reduced L-ornithine cooperativity. In the presence of spermidine,
the L-ornithine saturation curve became increasingly sigmoidal, the Hi
ll coefficient shifting from 2.5 in the absence of the inhibitor, to 3
.5 in the presence of 20 mM spermidine. The L-arginine analog, L-homoa
rginine, was also a substrate of the succinyltransferase, and the satu
ration of the enzyme by this substrate was also cooperative. All these
data confirmed the allosteric nature of the enzyme. Moreover, a mutan
t growing faster on L-ornithine than the parent strain had a modified
succinyltransferase with a reduced L-ornithine cooperativity. The fate
of L-homoarginine was different depending on whether the succinyltran
sferase was induced or not; excreted succinylhomoarginine was found in
cultures induced for the transferase activity whereas guanidinovalera
te was excreted in non-induced cultures. The 'waste' of succinyl CoA,
which could not be regenerated from the excreted succinylhomoarginine,
explained the inhibition exerted by L-homoarginine on growth when orn
ithine or arginine was used as the growth medium.