L-citrulline is an important marker to many diseases. A simple, accurate and rapid enzymatic method is proposed for the determination of L-citrulline for its bioconversion by the ornithine transcarbamoylase (EC2. 1.3.3) and the carbamate kinase (EC 2.7. 2.2). The optimized conditions for the bioconversion were 30 degrees C similar to 35 degrees C, pH 6 similar to 7. The reserved special activity of immobilized enzymes was up to 95% after they were kept for 60 days in 4 degrees C. The linear range was 2 similar to 10 mg/L (R =0. 9987), the recovery for the detrmination was more than 99%. The enzymatic method is simple and accurate. It has been applied successfally to the determination of urinary L-citrulline from 3 sufferers of rheumatoide arthritis.

L-Arginine can be converted to L-citrulline with arginine deiminase which was found in the Streptococcus faecalis.Many factors affecting on the enzymatic activity were studied.The result shows that the optimum conditions are as follows:the strain age 20 h,37 ℃,pH 6.0,ρ(cetyltrimethylammonium bromide(CTAB))=0.30 g/L.Some metal ions such as Cu~(2+),Zn~(2+)and Co~(2+) also have effect on the enzymatic activity.

A simple,accurate and rapid spectrophotometric method is proposed for the determination of L-citrulline in enzynatic conversion solution.The method is based on the absorbance of complex at 490 nm being proportional to L-citrulline concentrations.Effect of L-arginine,L-ornithine,buffer solution,the time of reaction and dosage of diacetylmonoxime on the determination of L-citrulline is also studied.The linear range is 0～0.04(mg/mL)(r=0.999),and the mean recovery is 99.58%.