Stabilization of Aspergillus parasiticus cytosine deaminase by immobilization on calcium alginate beads improved enzyme operational stability

Figures & data

Figure 1.  Specific activity of free (0.0102 mg/mL) and immobilized (0.006 mg/mL) A. parasiticus cytosine deaminase.

Figure 2.  Effect of pH on immobilized A. parasiticus cytosine deaminase activity.

Figure 3.  Effect of temperature on immobilized A. parasiticus CD (0.006 mg/mL/bead) activity showing an optimum temperature of 50°C.

Figure 4.  Operational stability of immobilized A. parasiticus CD at 37°C. Residual activity of CD was 56% after 2 h. Of incubation and it dropped to zero at 12 h.

Figure 5.  Arrhenius plot for immobilized A. parasiticus cytosine deaminase.

Table 1.  Kinetics of immobilized A. parasiticus CD with cytosine and 5-fluorocytosine as substrates.

Kinetic parameters	Cytosine	5-fluorocytosine
K′M (mM)	0.60 ± 0.02	0.65 ± 0.03
V′max (µmol/min)	3.27 ± 0.32	0.024 ± 0.01
Kcat (S^−1)	545 ± 5.60	4.00 ± 0.50

Values are mean ± SD for triplicate determination.