Enzymes in cancer. Asparaginase from chicken liver

Abstract

A procedure for partial purification of asparaginase from chicken liver is presented. The bulk of the enzyme is located in the soluble fraction of chicken liver. Molecular weights of chicken-liver asparaginase and of the guinea-pig serum enzyme, estimated by gel filtration, were 306000 and 210000 respectively. The Michaelis constants (Km) at 37 degrees and pH 8- 5 were 6- 0 X 10-5 [image] and 7- 2 X10-5 [image] respectively. At 50 degrees the chicken-liver enzyme was moderately stable, some activity being lost by aggregation; in dilute electrolyte solutions the activity rapidly dimished. The anti-lymphoma effect of guinea-pig serum in mice carrying the 6C3HED tumour was confirmed. Chicken-liver asparaginase also showed an effect but in this case the enzyme preparation had to be administered repeatedly. Guinea-pig serum asparaginase was stable for several days in mouse blood, after intraperitoneal injection, whereas chicken-liver asparaginase rapidly disappeared. Aspartic acid [beta] -hydrazide was shown to be a competitive inhibitor of chicken-liver asparaginase with Ki approx. 5-6X 10-4 [image]. In mice it produced an anti-lymphoma effect, as reported previously.