Characterization of a novel metallocarboxypeptidase from Streptomyces cinnamoneus TH-2

Abstract

Carboxypeptidases are exopeptidases that catalyze the release of amino acids from the C-terminus of peptides or proteins. The peptides consisting of hydrophobic amino acids taste bitter. Therefore, the hydrolytic capability of carboxypeptidase toward hydrophobic amino acids at the C-terminus of peptides is useful for the degradation of bitter peptides. Using the genome data of Streptomyces cinnamoneus TH-2, we expressed and characterized a novel metallocarboxypeptidase (TH2-CP) in Streptomyces lividans. TH2-CP had a molecular mass of 37.7 kDa. As TH2-CP possesses a zinc-binding consensus motif (HXXE……H) and N-terminal prosegment residues, we suggest that TH2-CP could be classified into the M14A subfamily. In the presence of Z-Gly-Leu as the substrate, TH2-CP showed optimum activity at pHs 7 and 8 in potassium phosphate and Tris–HCl buffers, respectively. The optimum temperature for activity was 51 °C. Furthermore, 50 % activity was conserved after incubation at 38 °C for 30 min. TH2-CP showed broad substrate specificity, with a preference for hydrophobic amino acids, as demonstrated by casein hydrolysate breakdown. A novel metallocarboxypeptidase, TH2-CP, from S. cinnamoneus TH-2 was characterized. TH2-CP preferred substrates with hydrophobic amino acids at the C-terminal position for casein peptides. This property indicates that TH2-CP can be used to decrease the bitterness of peptides in food industries.