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L-asparagine degradation I

L-asparagine can serve as the sole source of carbon and nitrogen for E. coli . Asparaginase hydrolyzes L-asparagine, generating ammonia and L-aspartate. E. coli encodes three enzymes with asparaginase activity . However, only one of them, : ANSA-CPLX, has been shown to be required for utilization of L-asparagine. This cytoplasmic enzyme does not appear to be regulated at the level of transcription, but it is allosterically activated by L-asparagine , thus ensuring that L-asparagine is only utilized as a source of carbon and nitrogen when excess amounts beyond the normal protein synthesis requirements are available. A second cytoplasmic enzyme, : CPLX0-263, has only low levels of asparaginase activity and may thus not normally be involved in this process. The periplasmic asparaginase, : ANSB-CPLX, is highly active. Its expression is induced by anaerobiosis via Fnr, indicating that its primary function may be the generation of fumarate as an electron acceptor during anaerobic respiration . Interestingly, this enzyme has been used as a treatment for cancer . In humans, asparaginase causes rapid decline of plasma and cerebrospinal fluid L-asparagine levels when administered to patients with acute lymphoblastic leukemia, resulting in selective toxicity to malignant lymphoblasts, which have a relatively high nutritional requirement for this amino acid. Review: Reitzer, L. Catabolism of Amino Acids and Related Compounds, Module 3.4.7

from BIOCYC source record: ECO_ASPARAGINE-DEG1-PWY
Type: pathway
Taxonomic scope
:
organism-specific biosystem
Organism
:
Escherichia coli
BSID:
547602

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