Ch. 25: Glycogen Synthesis

Uridine Diphosphate-Glucose (UDP-Glucose)

a high energy form of glucose and glucose donor in glycogen synthesis, synthesized by UDP-glucose phosphorylase, hydrolyzes UTP to release pyrophosphate and subsequent PPi hydrolysis

glycogen synthase

transfers glucose moiety from UDP-glucose to C4 nonreducing terminal end of the glycogen chain, forming alpha-1,4 glycosidic bond, this is a regulatory step in glycogen synthesis

glycogenin

synthesizes primer oligosaccharide chain, present in glycogen

branching enzyme

facilitates branching of glycogen synthesis by breaking alpha-1,4 linkages and taking approximately 7 glucose residues and synthesizing at alpha-1,6 glycosidic bond

reciprocal regulation

glycogen synthesis is inhibited by the same glucagon/epinephrine cascade that stimulate glycogen breakdown

it stimulates this process by phosphorylating/activating the phosphorylase kinase

how does PKA regulate glycogen degradation

it inhibits glycogen synthesis by phosphorylating/inactivating glycogen synthase

how does PKA regulate glycogen synthesis

protein phosphatase 1 (PP1)

removes phosphoryl groups to reverse effects on enzymes in glycogen metabolism, shifts glycogen metabolism to synthesis mode