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BIO NMDCAT Carbohydrates
nmdcat.online June 27, 2026

In plants, the formation of starch granules involves the coordinated action of starch synthase (for α-1,4 chain extension) and branching enzyme. The branching enzyme creates α-1,6 linkages by

A. Hydrolyzing an α-1,4 bond and then re-forming an α-1,6 bond with a different sugar
B. Cleaving a short α-1,4-linked oligosaccharide chain from one location and transferring it to the C-6 hydroxyl of a glucose in another chain
✓
C. Activating glucose with UTP and then linking it to a C-6 hydroxyl
D. Phosphorylating the C-6 position to make it susceptible to nucleophilic attack

📝 Explanation

Branching enzyme is a transglycosylase. It cuts a short α-1,4-linked chain of 6-7 glucose units and transfers it to the 6-OH position of a glucose residue in the same or a nearby chain. This creates the α-1,6 branch points characteristic of amylopectin and glycogen.

📖 Additional Information

  • Hydrolyzing an α-1,4 bond and then re-forming an α-1,6 bond with a different sugar
  • Cleaving a short α-1,4-linked oligosaccharide chain from one location and transferring it to the C-6 hydroxyl of a glucose in another chain
  • Activating glucose with UTP and then linking it to a C-6 hydroxyl
  • Phosphorylating the C-6 position to make it susceptible to nucleophilic attack

Branching enzyme is a transglycosylase. It cuts a short α-1,4-linked chain of 6-7 glucose units and transfers it to the 6-OH position of a glucose residue in the same or a nearby chain. This creates the α-1,6 branch points characteristic of amylopectin and glycogen.

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