scholarly journals Control of L-ornithine specificity in Escherichia coli ornithine transcarbamoylase. Site-directed mutagenic and pH studies.

1991 ◽  
Vol 266 (28) ◽  
pp. 18626-18634 ◽  
Author(s):  
J.O. Goldsmith ◽  
S. Lee ◽  
I. Zambidis ◽  
L.C. Kuo
1982 ◽  
Vol 79 (7) ◽  
pp. 2250-2254 ◽  
Author(s):  
L. C. Kuo ◽  
W. N. Lipscomb ◽  
E. R. Kantrowitz

1984 ◽  
Vol 224 (2) ◽  
pp. 379-388 ◽  
Author(s):  
M D Templeton ◽  
P A Sullivan ◽  
M G Shepherd

The mechanism of inhibition of ornithine transcarbamoylase by the bacterial toxin phaseolotoxin [N-delta-(phosphosulphamyl)ornithylalanylhomoarginine] was investigated. Ornithine transcarbamoylase was purified by affinity chromatography from Escherichia coli W argR- by using N-delta-(phosphonoacetyl)ornithine as the ligand. Under steady-state conditions phaseolotoxin inhibition was reversible and exhibited mixed kinetics with respect to carbamoyl phosphate. The apparent Ki and apparent K'i were 0.2 microM and 10 microM respectively. Inhibition with respect to ornithine was noncompetitive, with an apparent Ki of 0.9 microM. These data are consistent with competitive binding of phaseolotoxin to the carbamoyl phosphate-binding site of the enzyme. The toxin also appears to be able to bind to the enzyme-carbamoyl phosphate complex, although, since K'i is 50 times greater than Ki, this event is kinetically much less significant. In the presence of phaseolotoxin ornithine transcarbamoylase exhibited a transient phase of activity before a steady state. This is consistent with low rates of association and dissociation for the toxin with enzyme and the enzyme-toxin complex. Rate constants of 2.5 × 10(4)M−1 × s−1 and 5 × 10(−3)s−1 were estimated for the association and dissociation constants respectively.


PLoS ONE ◽  
2020 ◽  
Vol 15 (2) ◽  
pp. e0228487
Author(s):  
Lisa Ngu ◽  
Jenifer N. Winters ◽  
Kien Nguyen ◽  
Kevin E. Ramos ◽  
Nicholas A. DeLateur ◽  
...  

Sign in / Sign up

Export Citation Format

Share Document