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Distinct physiological roles for the two L-asparaginase isozymes of Escherichia coli.

Biochemical and biophysical research communications (2013-06-04)
Yogitha N Srikhanta, John M Atack, Ifor R Beacham, Michael P Jennings
ABSTRACT

Escherichia coli expresses two L-asparaginase (EC 3.5.1.1) isozymes: L-asparaginse I, which is a low affinity, cytoplasmic enzyme that is expressed constitutively, and L-asparaginase II, a high affinity periplasmic enzyme that is under complex co-transcriptional regulation by both Fnr and Crp. The distinct localisation and regulation of these enzymes suggest different roles. To define these roles, a set of isogenic mutants was constructed that lacked either or both enzymes. Evidence is provided that L-asparaginase II, in contrast to L-asparaginase I, can be used in the provision of an anaerobic electron acceptor when using a non-fermentable carbon source in the presence of excess nitrogen.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
L-Asparagine, ≥98% (HPLC)
Sigma-Aldrich
L-Asparagine, BioReagent, suitable for cell culture, suitable for insect cell culture
Sigma-Aldrich
Adenosine 3′,5′-cyclic monophosphate sodium salt monohydrate, ≥98.0% (HPLC), powder
Sigma-Aldrich
Adenosine 3′,5′-cyclic monophosphate, ≥98.5% (HPLC), powder
Supelco
L-Asparagine, certified reference material, TraceCERT®