Phosphorylation of sucrose synthase from maize seedlings.
Two isoforms of sucrose synthase (SS1 and SS2) from maize (Zea mays, var. Mona) seedlings co-purified with a calcium and phospholipid dependent protein kinase. The enzymatic preparation obtained gave a positive reaction with the antibody against mammalian protein kinase C. Maize sucrose synthase was phosphorylated by the endogenous protein kinase. Also, mammalian protein kinases (protein kinase C and protein kinase A) were able to phosphorylate the 86 kDa subunit of sucrose synthase. When excised seedlings were fed [32P]orthophosphate, sucrose synthase was also phosphorylated. Microsequencing of in vivo labelled enzyme has shown phosphorylation of Ser-15 in SS2. The present work provides evidence that maize sucrose synthase is the physiological substrate of the endogenous calcium and phospholipid dependent protein kinase(s).
Lindblom
S
S
Department of Medical and Physiological Chemistry, Biomedical Centre, Uppsala, Sweden.
Ek
P
P
Muszyńska
G
G
Ek
B
B
Szczegielniak
J
J
Engström
L
L
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005964:Glucosyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008322:Mammals; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D012694:Serine / Q000737:chemistry; D013379:Substrate Specificity; D003313:Zea mays / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development
D007527:Isoenzymes; D012694:Serine; D005964:Glucosyltransferases; C022699:sucrose synthase; D011494:Protein Kinases