Vitreoscilla hemoglobin expressing Enterobacter aerogenes and Pseudomonas aeruginosa respond differently to carbon catabolite and oxygen repression for production of L-asparaginase,an enzyme used in cancer therapy

摘要

The production of antileukemic enzyme L-asparaginase in two distinctly related bacteria,Enterobacter aerogenes,Pseudomonas aeruginosa,and in their recombinants expressing the Vitresocilla hemoglobin(VHb)has been studied.Both bacteria showed a substantially different degree of carbon catabolite repression of the enzyme production.E.aerogenes grown under catabolite repression had more than 20-fold lower L-asparaginase activity than the controls.This figure was only 1.6-fold for P.aeruginosa.In the medium with restricted nutrient content,however,the inhibitory effect of glucose on the enzyme production was less pronounced.The presence of VHb,an efficient oxygen uptake system,had also different effects in both bacteria.Under conditions of no catabolite repression,this protein caused about 7-fold lower L-asparaginase activity in E.aerogenes,but similar or even slightly stimulatory effect in P.aeruginosa.The use of a relatively poor carbon source,mannitol,caused a lower L-asparaginase level and no glucose type catabolite repression.