Physiology and kinetics of a new L-Asparaginase from arthrobacter citreus

ABSTRACT

active intracellular L-asparagnase was detected in cultures of Arthrobacter citreus. The enzyme was farmed constitutively on a variety of media irrespective to the presence of the substrate or other structurally-related compounds. Glucose severely suppressed the enzyme formation The study of the physiology of formation has revealed that this enzyme reaches the maximum level at the end of the exponential phase and the beginning of stationary phase of growth followed by a rapid decline of the enzyme level upon further aging of the culture. The enzyme, obtained from the cells by benzene extraction. exhibited optimum activity at pH 3 and had an apparent KM 1.6 x l0-2M with respect to L- asparagire substrate. A significant substrate - protective effect was noted against heat iractivation of the enzyme at least up to 70§. The enzyme showed high specificity for L- asparagire and L- glutaminc with little or no activity on other amides tested. Significant activation was noted for magnesium ion whereas ferrous exhibited strong inhibitory effect. The properties of this enzyme are discussed in the light of possible application in cancer therapy