Xiaohang Ma

Purification and characterization of a cis-epoxysuccinic acid hydrolase from Bordetella sp. strain 1–3

Purification of a cis-epoxysuccinic acid hydrolase was achieved by ammonium sulfate precipitation, ionic exchange chromatography, hydrophobic interaction chromatography followed by size-exclusion chromatography. The enzyme was purified 177-fold with a yield of 14.4%. The apparent molecular mass of the enzyme was determined to be 33kDa under denaturing conditions. The optimum pH for enzyme activity was 7.0, and the enzyme exhibited maximum activity at about 45 degrees C in 50mM sodium phosphate buffer (pH 7.5). EDTA and o-phenanthrolin inhibited the enzyme activity remarkably, suggesting that the enzyme needs some metal cation to maintain its activity. Results of inductively coupled plasma mass spectrometry analysis indicated that the cis-epoxysuccinic acid hydrolase needs Zn(2+) as a cofactor. Eight amino acids sequenced from the N-terminal region of the cis-epoxysuccinic acid hydrolase showed the same sequence as the N-terminal region of the beta subunit of the cis-epoxysuccinic acid hydrolase obtained from Alcaligenes sp.

Isolation of a homocysteine γ-lyase-producing bacterium and study of its enzyme production conditions

Aim:  To investigate the possibility of finding a new homocysteine (Hcy) γ‐lyase with the desired properties for Hcy measurement in bacteria.