Microassay methods for taurine and cysteine sulfinate decarboxylase activity.

Microassay methods for taurine (2-aminoethanesulfonic acid) and cysteine sulfinate decarboxylase (CSD: EC 4.1.1.29) have been developed. Cation exchange resin (Dowex 50W x 8, 200--400 mesh) was used for the separation of taurine from other fluorescamine reactive substances. The "taurine fraction" in this column chromatographic procedure was collected and fluorescence development was carried out. The maximal sensitivity obtained for taurine was 25 pmoles. The specificity, reproducibility, sensitivity and recovery for taurine obtained by this method were satisfactory enough to be used for biological applications. The activity of CSD was determined by measuring the formation of 14CO2 from DL-[1-14C]-cysteine sulfinic acid using a specially designed micro-vessel. The activity in cerebral tissues containing 5 microgram of protein was accurately detected by this microradiometrical method. Using above microassay methods for taurine and CSD activity, it was found that in the rat spinal cord, taurine is distributed rather evenly, whereas the distribution of CSD activities is uneven and the highest activity is localized at the dorsal part of the dorsal horn.