Protein phosphorylation as a mechanism for regulation of spinach leaf sucrose-phosphate synthase activity

Joan L.A. Huber, Steven C. Huber, Tom Hamborg Nielsen

Research output: Contribution to journalArticle

Abstract

Studies were conducted to determine whether protein phosphorylation may be a mechanism for regulation of spinach (Spinacia oleracea L.) leaf sucrose-phosphate synthase (SPS), shown previously to be light-dark regulated by some type of covalent modification. Radioactive phosphate was incorporated into the 120-kDa subunit of SPS during labeling of excised leaves with [32P]Pi, as shown by immunoprecipitation and denaturing gel electrophoresis of the enzyme. Conditions which activated the enzyme (illumination of leaves or mannose treatment of leaf discs in darkness) reduced the incorporation of radiolabel into SPS in the in vivo system. The partially purified SPS protein could also be phosphorylated in vitro using [γ-32P]ATP. In the in vitro system, the incorporation of radiolabel into the 120-kDa subunit of SPS was dependent on time and magnesium concentration, and was closely paralleled by inactivation of the enzyme. These results provide the first evidence to establish protein phosphorylation as a mechanism for the covalent regulation of SPS activity.

Original languageEnglish (US)
Pages (from-to)681-690
Number of pages10
JournalArchives of Biochemistry and Biophysics
Volume270
Issue number2
DOIs
StatePublished - May 1 1989

Fingerprint

sucrose-phosphate synthase
Phosphorylation
Spinacia oleracea
Proteins
Enzymes
Darkness
Mannose
Electrophoresis
Lighting
Immunoprecipitation
Labeling
Magnesium
Adenosine Triphosphate
Gels
Phosphates
Light

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology

Cite this

Protein phosphorylation as a mechanism for regulation of spinach leaf sucrose-phosphate synthase activity. / Huber, Joan L.A.; Huber, Steven C.; Nielsen, Tom Hamborg.

In: Archives of Biochemistry and Biophysics, Vol. 270, No. 2, 01.05.1989, p. 681-690.

Research output: Contribution to journalArticle

Huber, Joan L.A. ; Huber, Steven C. ; Nielsen, Tom Hamborg. / Protein phosphorylation as a mechanism for regulation of spinach leaf sucrose-phosphate synthase activity. In: Archives of Biochemistry and Biophysics. 1989 ; Vol. 270, No. 2. pp. 681-690.
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