Purification and properties of rat brain cysteine sulfinate decarboxylase (EC 4.1.1.29)

Rat brain cysteine sulfinate decarboxylase (EC 4.1.1.29), a key enzyme in taurine biosynthesis, has been separated from glutamate decarboxylase (EC 4.1.1.15) associated activity and purified to apparent homogeneity. The monomeric enzyme of molecular weight 70,000 +/- 2,000 exhibits half-maximal velocity with 90 +/- 40 ? M cysteine sulfinate or approximately 200 ? M cysteate and very high affinity towards pyridoxal phosphate but is unable to decarboxylate glutamate and aspartate. As specific enzyme activity represents approximately 20% of the total activity of the brain homogenate, measurements of total activity are discussed with regard to its use as a marker of taurine biosynthesis in brain.