Table 3.

Characterization of the Rubrobacter xylanophilus UGTCase activity

Reaction mixture composition	Assay temperature	Specific activity c (μmol min-1 mg-1)
25 mM potassium arsenate pH 6.8, 20 mM allantoate	37°C	0.046 ± 0.007 a
25 mM Hepes pH 6.8, 20 mM allantoate	37°C	n.d. a
50 mM potassium phosphate pH 6.8, 20 mM allantoate, 5 mM ornithine, EcOTCase (100 units)	37°C	0.050 ± 0.002 b
25 mM Hepes pH 6.8, 20 mM allantoate, 5 mM ornithine, EcOTCase (100 units)	37°C	n.d. b
50 mM potassium phosphate pH 6.8, 5 mM ornithine, EcOTCase (100 units)	37°C	n.d. b
50 mM potassium phosphate pH 6.8, 20 mM allantoate, 5 mM ornithine, EcOTCase (100 units)	60°C	5.913 ± 0.584 b
50 mM potassium phosphate pH 6.8, 5 mM ornithine, EcOTCase (100 units)	60°C	n.d. b

^aassessed by quantifying ureidoglycine.

^bassessed by quantifying citrulline.

^cData are the mean ± SD from at least three independent experiments. n.d., not detectable as defined in Methods.