TY  - JOUR
A1  - Ruzanski, Christian
A1  - Smirnova, Julia
A1  - Rejzek, Martin
A1  - Cockburn, Darrell
A1  - Pedersen, Henriette L.
A1  - Pike, Marilyn
A1  - Willats, William G. T.
A1  - Svensson, Birte
A1  - Steup, Martin
A1  - Ebenhöh, Oliver
A1  - Smith, Alison M.
A1  - Field, Robert A.
T1  - A bacterial glucanotransferase can replace the complex maltose metabolism required for starch to sucrose conversion in leaves at night
JF  - The journal of biological chemistry
N2  - Controlled conversion of leaf starch to sucrose at night is essential for the normal growth of Arabidopsis. The conversion involves the cytosolic metabolism of maltose to hexose phosphates via an unusual, multidomain protein with 4-glucanotransferase activity, DPE2, believed to transfer glucosyl moieties to a complex heteroglycan prior to their conversion to hexose phosphate via a cytosolic phosphorylase. The significance of this complex pathway is unclear; conversion of maltose to hexose phosphate in bacteria proceeds via a more typical 4-glucanotransferase that does not require a heteroglycan acceptor. It has recently been suggested that DPE2 generates a heterogeneous series of terminal glucan chains on the heteroglycan that acts as a glucosyl buffer to ensure a constant rate of sucrose synthesis in the leaf at night. Alternatively, DPE2 and/or the heteroglycan may have specific properties important for their function in the plant. To distinguish between these ideas, we compared the properties of DPE2 with those of the Escherichia coli glucanotransferase MalQ. We found that MalQ cannot use the plant heteroglycan as an acceptor for glucosyl transfer. However, experimental and modeling approaches suggested that it can potentially generate a glucosyl buffer between maltose and hexose phosphate because, unlike DPE2, it can generate polydisperse malto-oligosaccharides from maltose. Consistent with this suggestion, MalQ is capable of restoring an essentially wild-type phenotype when expressed in mutant Arabidopsis plants lacking DPE2. In light of these findings, we discuss the possible evolutionary origins of the complex DPE2-heteroglycan pathway.
KW  - Carbohydrate Metabolism
KW  - Computer Modeling
KW  - Metabolic Regulation
KW  - Oligosaccharide
KW  - Plant Biochemistry
KW  - Glucanotransferase
KW  - Leaf Cell
KW  - Maltose Metabolism
KW  - Starch Degradation
Y1  - 2013
U6  - https://doi.org/10.1074/jbc.M113.497867
SN  - 0021-9258
SN  - 1083-351X
VL  - 288
IS  - 40
SP  - 28581
EP  - 28598
PB  - American Society for Biochemistry and Molecular Biology
CY  - Bethesda
ER  -