In this study, a pH-induced morphological transition from micelles to vesicles for an amphiphilic photo cross-linkable biocopolymer (Az-NaCMCS), synthesized by mixing azidobenzaldehyde (Az) and an aqueous solution of carboxymethyl chitosan sodium salt (NaCMCS), was used for encapsulation of l-arginine deiminase (ADI). The aqueous solution of enzyme-loaded vesicles obtained was followed by UV-irradiation to result in shell cross-linked enzyme nanoreactors. The nanoreactors were characterized by TEM and DLS. Its encapsulation efficiency and loading capacity were determined. The encapsulation process showed no effect on the activity of ADI. The cross-linked shell of nanovesicles exhibited permeability to the substrate and product. The nanoreactors are enzymatically active and stable in blood plasma at 37°C. The in vitro growth inhibitory activity against MH134 cells showed almost the same dose-response profile as that of the native ADI. The nanoreactors exhibit the potential for arginine deprivation in cancer therapy.