Thermal stability and enzymatic activity of a smaller lysozyme from silk moth (Bombyx mori)

Bombyx mori lysozyme is 10 amino acids shorter than hen egg-white lysozyme, which is a typical c-type lysozyme. It was expressed by using the methylot rophic yeast Pichia pastoris. The thermal stability and the enzymatic activ ity of the Bombyx mori lysozyme were estimated and compared with those of h uman and hen egg-white lysozymes. The denaturation temperature was 17-26 de greesC lower than those of human and hen egg-white lysozymes. Further, the enthalpy change and the heat capacity change for unfolding were smaller tha n those of human lysozyme. It was also confirmed that the stability against guanidine hydrochloride was lower than those of the other two lysozymes. T he enzymatic activity toward a simple synthetic substrate was measured and compared with those of human and hen egg-white lysozymes. The B-F binding m ode was obviously dominant, although the A-E binding mode was preferred in human and hen egg-white lysozymes.