Huang S.-H.,Key Laboratory of Tea Biochemistry and |
Ma W.,Key Laboratory of Tea Biochemistry and |
Zhang P.-P.,Anhui Agricultural University |
Zhang J.-Y.,Anhui Agricultural University |
And 2 more authors.
European Journal of Entomology | Year: 2011
Pyridoxal kinase (PLK; EC 188.8.131.52) is a key enzyme in the metabolism of vitamin B 6 (VB 6) in Bombyx mori. A fusion expressional vector pET-22b-BPLK-His was constructed using a sub-cloning technique, the recombinant B. mori PLK was then expressed in Escherichia coli, purified and characterized. Bioinformatics were used to deduce the protein structure and genomic organization of this enzyme. Using Ni Sepharose affinity column chromatography, the recombinant protein was purified to very high degree (approximately 90%). The recombinant PLK exhibits a high specific enzymatic activity (1800 nmol/min/mg of protein). The maximum catalytic activity of this enzyme was recorded over a narrow pH range (5.5-6.0) and Zn 2+ is the most effective cation for catalysis under saturating substrate concentrations. When only triethanolamine is present as the cation, K + is an activator of PLK. A double reciprocal plot of initial velocity suggests that the enzyme catalyses the reaction by means of a sequential catalytic mechanism. Under optimal conditions, the Km value for the substrates of ATP and pyridoxal are 57.9 ± 5.1 and 44.1 ± 3.9 μM. B. mori's genome contains a single copy of the PLK gene, which is 7.73 kb long and contains five exons and four introns, and is located on the eighth chromosome. The PLK may be a dimer with two identical subunits under native conditions, and it is hypothesized that each monomer contains eight α-helices (α 1-8), nine β-strands (β1-9) and two segments of 3 10 helices.