A novel autophosphorylation mediated regulation of nitrite reductase in Candida utilis

  • Sengupta S
  • Subbarao Shaila M
  • Ramananda Rao G
  • 5

    Readers

    Mendeley users who have this article in their library.
  • 5

    Citations

    Citations of this article.

Abstract

The assimilatory nitrite reductase catalyses the conversion of nitrite to ammonia. The enzyme from Candida utilis has been previously purified to homogeneity and shown to be a heterodimer consisting of 58 kDa and 66 kDa subunits. The enzyme has also been shown to be induced by nitrate and repressed by ammonium ions. The levels of nitrite reductase mRNA, its protein and the enzyme activity were modulated together indicating that the primary level of regulation of this enzyme existed at the transcriptional level. Here we report that the 58 kDa and 66 kDa subunits of the enzyme were differentially phosphorylated under the induced and repressed conditions, indicating a second level of regulation. The highly phosphorylated 66 kDa subunit was shown to be dephosphorylated by calf intestinal alkaline phosphatase. The enzymatic activity associated with the native enzyme also decreased due to the dephosphorylation. Each of the subunits could undergo autophosphorylation at serine/threonine residues as demonstrated by thin layer chromatography and recognition by antibodies to phosphoamino acids. The presence of similar phosphorylated subunits under in vivo conditions has also been demonstrated. A model has been proposed to explain the posttranslational regulation of the enzyme.

Author-supplied keywords

  • Candida utilis
  • Nitrite reductase
  • Phosphorylation
  • Post-translational control
  • Regulation

Get free article suggestions today

Mendeley saves you time finding and organizing research

Sign up here
Already have an account ?Sign in

Find this document

Authors

  • Sagar Sengupta

  • Melkote Subbarao Shaila

  • Gannamani Ramananda Rao

Cite this document

Choose a citation style from the tabs below

Save time finding and organizing research with Mendeley

Sign up for free