Treponema denticola cystalysin catalyzes β-desulfination of L-cysteine sulfinic acid and β-decarboxylation of L-aspartate and oxalacetate

Pyridoxal 5'-phosphate-dependent cystalysin from Treponema denticola catalyzes the beta-displacement of the beta-substituent from both L-aspartate and L-cysteine sulfinic acid. The steady-state kinetic parameters for beta-desulfination Of L-cysteine sulfinic acid, k(cat) and K-m, are 89 +/- 7 s(-1) and 49 +/- 9 mM, respectively, whereas those for beta-decarboxylation Of L-aspartate are 0.8 +/- 0.1 s(-1) and 280 70 mM. Moreover, cystalysin in the pyridoxamine 5'-phosphate form has also been found to catalyze beta-decarboxylation of oxalacetate as shown by consumption of oxalacetate and a concomitant production of pyruvate. The k(cat) and K-m of this reaction are 0.15 +/- 0.01 s(-1) and 13 +/- 2 mM, respectively. Possible mechanistic and physiological implications are discussed. (C) 2003 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.