Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Pivot Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Target Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Query: EC:6.3.4.6 (
urease
)
7,490
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
A pH-variation study of jack bean (Canavalia ensiformis)
urease
steady-state kinetic parameters and of the inhibition constant of boric acid, a
urease
competitive inhibitor, was performed using both noninhibitory organic (MES,
HEPES
and CHES) and inhibitory inorganic (phosphate) buffers, in an effort to elucidate the functions exercised in the catalysis by the ionizable groups of the enzyme active site. The results obtained are consistent with the requirement for three groups utilized by
urease
with pK(a)s equal to 5.3+/-0.2, 6.6+/-0.2 and 9.1+/-0.4. Based on the appearance of the ionization step with pK(a)=5.3 in v(max)-pH, K(M)-pH and K(i)-pH profiles, we assigned this group as participating both in the substrate binding and catalytic reaction. As shown by its presence in v(max)-pH and K(M)-pH curves, the obvious role of the group with pK(a)=9.1 is the participation in the catalytic reaction. One function of the group featuring pK(a)=6.6, which was derived from a two-maxima v(max)-pH profile obtained upon increasing phosphate buffer concentration, an effect the first time observed for
urease
-phosphate systems, is the substrate binding, another possible function being modulation of the active site structure controlled by the ionic strength. It is also possible that the pK(a)=6.6 is a merger of two pK(a)s close in value. The study establishes that regular bell-shaped activity-pH profiles, commonly reported for
urease
, entail more complex pH-dependent behavior of the
urease
active site ionizable groups, which could be experimentally derived using species interacting with the enzyme, in addition to changing solution pH and ionic strength.
...
PMID:Jack bean (Canavalia ensiformis) urease. Probing acid-base groups of the active site by pH variation. 1602 57
Enzyme-powered motors self-propel through the catalysis of
in situ
bioavailable fuels, which makes them excellent candidates for biomedical applications. However, fundamental issues like their motion in biological fluids and the understanding of the propulsion mechanism are critical aspects to be tackled before a future application in biomedicine. Herein, we investigated the physicochemical effects of ionic species on the self-propulsion of
urease
-powered micromotors. Results showed that the presence of PBS, NaOH, NaCl, and
HEPES
reduced self-propulsion of
urease
-powered micromotors pointing towards ion-dependent mechanisms of motion. We studied the 3D motion of
urease
micromotors using digital holographic microscopy to rule out any motor-surface interaction as the cause of motion decay when salts are present in the media. In order to protect and minimize the negative effect of ionic species on micromotors' performance, we coated the motors with methoxypolyethylene glycol amine (mPEG) showing higher speed compared to noncoated motors at intermediate ionic concentrations. These results provide new insights into the mechanism of
urease
-powered micromotors, study the effect of ionic media, and contribute with potential solutions to mitigate the reduction of mobility of enzyme-powered micromotors.
...
PMID:Ionic Species Affect the Self-Propulsion of Urease-Powered Micromotors. 3280 69
