Bacillus fastidiosus

The reaction can be observed in either the kinetic or the equilibrium mode. The Bacillus fastidiosus enzyme has the highest Michaelis constant (1.0 x 10" mol/L) and the hog fiver has the lowest (1,7 x 10 mol/L), the choice of enzyme influencing the incubation period required to reach equilibrium and the conditions for a pseudo first-order Idnetic approach. The decrease of absorbance as urate is converted may be monitored by a spectrophotometer at 293 nm and this forms the basis of a proposed reference procedure. However, at this wavelength, most of the absorbance is due to plasma proteins. Therefore there is a high signal-noise ratio, which can compromise the precision of the method. A high quality spectrophotometer with narrow bandpass is required and this is rarely satisfied with automated analyzers. 

Uricase from Bacillus fastidiosus A.T.C.C. 29604 has high Km to facilitate predicting Ab (Zhang, et al, 2010 Zhao, Y.S., et al, 2006, 2009). Reaction curves at low levels of uric acid with this uricase at 40 U/L are demonstrated in Fig. 3. Steady-state reaction is not reached within 30 s since reaction initiation it is difficult to get more than 5 data with absorbance changes over 0.003 for kinetic analysis of reaction curve at uric acid levels below 3.0 (imol/L. At 40 U/L of this uricase, the absorbance after reaction for 5.0 min has negligible difference from that after reaction for 30 min for uric acid below 5.0. imol/L. To quantify the difference between Ao and Ab after reaction for 5.0 min, the equilibrium method has an upper limit of about 5.0 imol/L, while kinetic analysis of reaction curve with Km as a constant is feasible for So of about 5.0 imol/L. Thus, the change of absorbance over 0.050 between Ao and the absorbance after reaction for 5.0 min can be the switch threshold to change from the equilibrium method to kinetic analysis of reaction curve. 

Effects of modification of amino groups with pwlyfethylene glycol) on a recombinant uricase from Bacillus fastidiosus. Bioscience Biotechnology Biochemistry, 2010 vol. 74, no.6, Qune 2010), pp. 1298-1301,0916-8451. ISSN 0916-8451. 

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