Biochemical characterization of a metagenome-derived decarboxylase

The metagenomic library screening approach has broadened the field of enzymology, leading to the identification of a wider range of natural biocatalysts. Based on cloning a novel cysteine decarboxylase gene (undec1A) from soil metagenome, we presented a detailed study of the biochemical properties of the recombinant Undec1A protein with a high performance liquid chromatography method and automatic amino acid analyzer method using l-cysteine as the substrate. We found that the maximum activity for the decarboxylase occurred at pH 7.0 and 35 °C. The decarboxylase had an apparent Km value of 0.59 mM, a Vmax value of 68.5 μM/min and a kcat value of 4.57/min. We demonstrated that the active catalytic domain of Undec1A protein contained a potential Mg2+ binding site. Furthermore, through mutation analysis we found that the amino acid residues of His-30 in His insertion motif and Ser-113 in ACGD motif were necessary for the activity of Undec1A protein. The characterization of the biochemical properties of Undec1A enhanced our understanding of this novel decarboxylase isolated from uncultured soil microorganisms.