TY - JOUR
T1 - Protein phosphorylation as a mechanism for regulation of spinach leaf sucrose-phosphate synthase activity
AU - Huber, Joan L.A.
AU - Huber, Steven C.
AU - Nielsen, Tom Hamborg
N1 - Funding Information:
1 These are cooperative investigations of the U.S. Department of Agriculture, Agricultural Research Service, and the North Carolina Agricultural Research Service, Raleigh. This is paper No. 11971 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC 27695-7643. ’ To whom correspondence should be addressed at: USDA/ARS, Plant Science Research, 3127 Ligon Street, NC State University, Raleigh, NC 27607. ’ Collaborator via fellowship supported by OECD Project on Food Production and Preservation and by the Danish Veterinary and Agricultural Research Council, Grant 13-4047.
PY - 1989/5/1
Y1 - 1989/5/1
N2 - 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.
AB - 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.
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U2 - 10.1016/0003-9861(89)90551-1
DO - 10.1016/0003-9861(89)90551-1
M3 - Article
C2 - 2523212
AN - SCOPUS:0024671488
SN - 0003-9861
VL - 270
SP - 681
EP - 690
JO - Archives of Biochemistry and Biophysics
JF - Archives of Biochemistry and Biophysics
IS - 2
ER -