Enzymes of vitamin B6 degradation. Purification and properties of two N-acetylamidohydrolases.

摘要: Abstract alpha-(N-Acetylaminomethylene)succinic acid hydrolase (Compound A hydrolase, EC 3.5.1-) and alpha-hydroxymethyl-alpha'-(N-acetylaminomethylene)succinic B were purified to homogeneity from Pseudomonas MA-1 Arthrobacter Cr-7, respectively. The two inducible enzymes catalyze Reactions 1 2, respectively, which release the first generally useful anabolic intermediates during growth of these organisms with (formula; see text) pyridoxine as a sole source carbon nitrogen. Compound is monomeric protein Mr 32,500 aspartic its NH2-terminal residue. (Mr congruent 205,000) multimer containing probably six identical subunits glycine NH2 terminus. have quite different amino analyses, although both are high in Asx Glx, lack tryptophan, show similar stabilities pH temperature. has pI 4.4, Km 3.3 microM, Vmax 3.1 mumol X min-1 mg-1 at 6.5 25 degrees C; no analogue substrates found. 4.2, 3.8 C 7.0; it also hydrolyzes slowly. Both inhibited competitively by di- tricarboxylic acids, itaconic being among most effective. Sulfite inhibits time-dependent mechanism not yet understood. amidases appear differ greatly architecture despite similarity properties overall reactions they catalyze.