Synthesis of glucose oxidase-PEG aldehyde conjugates and improvement of enzymatic stability

Figures & data

Figure 1. HPLC chromatograms of GOD–PEG aldehyde conjugate (n_GOD/n_PEG 1:20) and free GOD.

Figure 2. Changes in FAD fluorescence intensities of native GOD and a GOD–PEG aldehyde conjugate (n_GOD/n_PEG 1:5) depending on time at 60 °C for different pH values, λ_ex= 400 nm, λ_em= 500 nm; pH 4 (A), pH 5 (B), pH 6 (C), pH 7 (D), pH 8 (E).

Figure 3. Thermal inactivation of the native and the conjugates (n_GOD/n_PEG 1:1; n_GOD/n_PEG 1:5) which incubated at 60 °C for different time.

Figure 4. Activities of native GOD and GOD–PEG aldehyde conjugate with different molar ratios (n_GOD/n_PEG 1/1, 1/5, 1/10, 1/20) depending on pH at 30 °C.

Figure 5. Thermal stabilities of GOD–PEG aldehyde conjugates with different molar ratios (n_GOD/n_PEG 1/1, 1/5, 1/10, 1/20) at pH 5.

Table 1. The kinetic parameters of the oxidation of glucose by GOD at pH 5.0.

Parameter	Native GOD	GOD–PEG aldehyde
Km (mM min^−1)	12.47 ± 0.09	8.92 ± 0.1
Vm (mM)	0.013 ± 0.001	0.01 ± 0.0
Kcat (min^−1)	5.13 ± 0.3	4 ± 0.01
Kcat/Km (1 mg^−1 min^−1)	0.411 ± 0.02	0.448 ± 0.03

Figure 6. SPM images of the free GOD (A) and modified GOD with PEG aldehyde (nE/nD:1/5) (B).

Figure 7. Storage stabilities of native and modified GOD with PEG aldehyde storage at 4 °C temperature.