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A novel autophosphorylation mediated regulation of nitrite reductase in Candida utilis

Sengupta, S and Shaila, MS and Rao, GR (1997) A novel autophosphorylation mediated regulation of nitrite reductase in Candida utilis. In: Febs Letters, 416 (1). pp. 51-56.

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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 me 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.

Item Type: Journal Article
Publication: Febs Letters
Publisher: Elsevier Science
Additional Information: Copyright of this article belongs to Elsevier Science.
Keywords: Nitrite reductase;regulation;post-translational control;phosphorylation;Candida utilis
Department/Centre: Division of Biological Sciences > Microbiology & Cell Biology
Date Deposited: 09 Feb 2010 11:51
Last Modified: 19 Sep 2010 05:01
URI: http://eprints.iisc.ac.in/id/eprint/18343

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