No abstract

Three thiazolium salts, 3-[2-(l-3-p-menthyloxy)ethyl]thiazolium bromide (1), 3-(l-3-p-menthyl)thiazolium halides (2), and 3-(l-3-p-menthyl)-4-methylthiazolium perchlorate (3) have been examined for the catalysis of benzoin condensation in micellar two-phase media. The catalytic activities on the chemical yields of benzoin were observed to be high for 1 and 2 but low for 3. On the contrary, for the asymmetric induction, 3 gave much higher optical purity of 35.3% than in the cases of 1 and 2 (0.8–3.5%). These results are discussed in terms of micellar and conformational effects.

N-carbamoyl-L-cysteine amidohydrolase (NCC amidohydrolase) was purified and characterized from the crude extract of Escherichia coli in which the gene for NCC amidohydrolase of Pseudomonas sp. strain ON-4a was expressed. The enzyme was purified 58-fold to homogeneity with a yield of 16.1% by three steps of column chromatography. The results of gel filtration on Sephacryl S-300 and SDS-polyacrylamide gel electrophoresis suggested that the enzyme was a tetramer protein of identical 45-kDa subunits. The optimum pH and temperature of the enzyme activity were pH 9.0 and 50 degrees, respectively. The enzyme required Mn(2+) ion for activity expression and was inhibited by EDTA, Hg(2+) and sulfhydryl reagents. The enzyme was strictly specific for the L-form of N-carbamoyl-amino acids as substrates and exhibited high activity in the hydrolysis of N-carbamoyl-L-cysteine as substrate. These results suggested that the NCC amidohydrolase is a novel L-carbamoylase, different from the known L-carbamoylases.

No abstract

No abstract