Characterization of cerebral cysteine sulfinic acid decarboxylase. Molecular parameters and inhibition studies

The molecular properties of cysteine sulfinic acid decarboxylase (EC 4.1.1.29) from calf brain were examined in a crude enzyme preparation. The Stokes radius (42 A) was determined by gel filtration and the sedimentation coefficient, s20,w (6.1 x 10(-13 s) by density gradient centrifugation. Calculation of the molecular weight and frictional ratio gave values of 73,000 and 1.52, respectively. beta-Mercaptopropionic acid and an arginine reagent, phenylglyoxal, were observed to be potent inhibitors of the enzyme. Pyridoxal phosphate, a cofactor of the decarboxylase, was observed to protect the enzyme against phenylglyoxal inhibition. This result indicates that an arginine residue may be located at the active site of cysteine sulfinic acid decarboxylase. The components of taurine metabolism gave little or no inhibition of the decarboxylase. Glutaric acid, malic acid and C-allylglycine, all widely known as potent inhibitors of glutamic acid decarboxylase, only slightly inhibited cysteine sulfinic acid decarboxylase.