A new quantitative analytical method of serum biotinidase activity using biocytin as a substrate and its clinical significance in Japan

We have developed a new quantitative analytical method of serum biotinidase activity, which uses the native substrate biocytin, and to which can be ap plied the improved agar plate method of biotin bioassay. Assay characterist ics were within acceptable ranges (intra-assay CVs, 4.44% and 1.95% at 1.82 +/- 0.08 and 3.08 +/- 0.06 pmol/min/ml; day-to-day CVI 5.92% at 2.68 +/- 0 .16 pmol/min/ml). The enzyme activity with biocytin was stable at 4 degrees C for 90 days. The mean value of the serum biotinidase levels in 129 health y adults was 2.71 +/- 0.93 pmol/min/ml. The method was clinically comparabl e with a colorimetric method for detection of biotinidase deficiency. Bioti n supplementation treatment normalized our partial biotinidase deficiency p atient's serum biotinidase activity. This normalized phenomenon has not yet been observed in a Caucasian patient, We also found that the distribution of the enzyme activities with biotinyl-p-aminobenzoate in 8 of 11 patients with suspected biotin metabolic disorders shifted to a higher level than th at of the controls. Although, we have few opportunities to analyze the sera of biotin metabolic disorders in Japan, the new method are suitable for cl inical research applications in combination with the colorimetric method. ( C) 2001 Elsevier Science B,V. All rights reserved.