Part:BBa_K2286012
HheC: halohydrin dehalogenase
This is a halohydrin dehalogenase from Agrobacterium radiobacterAD1(HheC). HheC is an important enzyme in the halide dehalogenation reaction, which catalyzes o-halide to epoxides and hydrogen halides through intramolecular nucleophilic substitution mechanism. So it can catalyze many substrates, such as 1,3-dichloro propanol (2,3-DCP), 2,3-dichloropropane-1-ol (2,3-DCP), 3-chloropropane-1,2-diol (CPD) and so on.
Sequence and Features
- 10COMPATIBLE WITH RFC[10]
- 12COMPATIBLE WITH RFC[12]
- 21COMPATIBLE WITH RFC[21]
- 23COMPATIBLE WITH RFC[23]
- 25INCOMPATIBLE WITH RFC[25]Illegal NgoMIV site found at 718
- 1000COMPATIBLE WITH RFC[1000]
Characterization
Molecular weight
This halohydrin dehalogenase gene codes for a protein of 762 amino acids with a molecular mass of 29kDa[2].
Structure of HheC: homologous tetramer
It is reported that halohydrin dehalogenase HheC is a symmetric tetramer that can be thought of as a dimer. The four active centers of HheC tetramer are centrosymmetric. The active sites include substrate binding sites and halide binding sites, surrounded by four Loop regions, loop1 (F12-Q87), Loop2 (A133 (373), Loop3 (P175-F188) and Loop4 (F243-P253), while the Ser132-Tyr145-Arg149 catalytic triad is contained in these four Loops. There is a synergistic effect between the amino acid residues on the four Loop regions, which are involved in the change of the active site conformation during the enzymatic catalysis. At the same time, it is reported that the C-terminus of the HheC plays an important role in its catalytic activity and thermal stability [1].
Michaelis constant of HheC toward 2,3-DCP
Michaelis constant of HheC at pH 8
Km=0.86642±0.10932mM Kcat=0.569±0.020S-1
Michaelis constant of HheC at pH 8.5
Km=3.03149±0.55904 mM Kcat=1.241±0.095 S-1
The results of pH 8 and pH 8.5 show that pH 8.5 is more suitable for HheC catalytic reaction of 2,3-DCP.
Michaelis constant of HheC toward CPD
Km=7.04277±2.07491mM Kcat=0.676±0.065 S-1
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