Abstract
An intracellular L-asparaginase with antitumour activity was purified from a strain of Citrobacter. The optimum conditions for enzyme production by fermentation on scales up to 2700 l were investigated. Highest enzyme yield was obtained in corn-steep liquor medium (9-2%, W/V) at 37 degrees C. Oxygen limitation was not necessary for high enzyme yield. A total recovery of 4-3% from nucleic-acid-free extract and a 180-fold increase in specific activity were obtained after purificaiton. The specific activity of the purified preparation was 45 i.u./mg protein. The enzyme hydrolysed D-asparagine and L-glutamine at 7 and 5%, respectively, of its activity toward L-asparagine, but L-glutaminase activity could be demonstrated only at substrate concentrations above 5 mM. The Km values for L-asparagine and D-asparagine were 2-6 X 10(-5) and 1-4 X 10(-4) respectively. The anti-lymphoma activity of the enzyme was demonstrated with Gardner lymphosarcoma and was found only slightly less potent that Crasnitin, the most active asparaginase so far tested in this system.
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