Properties of L-asparaginase in cell-free extracts of Streptomyces karnatakensis.

L-asparaginase was extracted from whole cells of Streptomyces karnatakensis by different procedures, including cell disintegration by ultra sonic waves and grinding with alumina. The specific activity of the enzyme in crude extracts was much lower than that in while cells. Optimum activity of the enzyme in crude extracts was obtained after an incubation time of 30 min at 38 degrees C in the presence of 16 micromole substrate/ml reaction mixture; the enzyme has an apparent Km value of 3.5 x 10(-3) M. The enzyme was inhibited by PCMB, indicating a requirement for a free sulfhydryl group. A competitive type of inhibition was noticed with D1-aspartic and a feed back type of inhibition was noticed with L-cysteine. The enzyme showed stereospecificity for L-asparagine, however, some activity was noticed with the D-isomer. This was discussed in terms of the biosynthesis of an isomerase.