Glycogen — synthesis (4) and breakdown (3), all available
G6P is stored as branched glycogen and later released as G1P / free glucose. Synthesis uses UDP-glucose. Breakdown is phosphorolysis, not hydrolysis, except the debranching glucosidase tab. PGM1 sits on both arms.
Phosphoglucomutase-1 PGM1 · isoform 2
α-G1P ⇌ α-G6P
Ping-pong phospho-relay on 6SNO. Crystal G1P + Zn; G6P is a 6SNQ overlay. Phospho-Ser is SEP135 — residue 117 is VAL on this occupancy. Both synthesis and breakdown use this page.
EC 5.4.2.2 · PDB 6SNO
▶ OPEN SIMULATORUDP-glucose pyrophosphorylase UGP2
G1P + UTP + H⁺ → UDPG + PPi
Nucleotidyl transfer on 4R7P. Occupancy is UDP-glucose (UPG); UTP, G1P, and PPi are schematic splits. Crystal Zn is crystallization, not physiological Mg.
EC 2.7.7.9 · PDB 4R7P
▶ OPEN SIMULATORGlycogenin-1 GYG1 · primer
Tyr-OH + UDPG + H⁺ → Glc-Tyr + UDP
Self-glucosylation on 3T7O. Attacking OH on this occupancy is partner-chain B Tyr197 — UniProt primer is Tyr195 (dimer hedge). Primer, not elongation.
EC 2.4.1.186 · PDB 3T7O
▶ OPEN SIMULATORGlycogen synthase GYS1 · muscle
glycogen(n) + UDPG + H⁺ → glycogen(n+1) + UDP
Elongation on 7Q13. Soak was UDP-glucose; occupancy is cleaved UDP + glucose. Crystal GLC is product-like, not glycogen(n). Liver GYS2 has no PDB.
EC 2.4.1.11 · PDB 7Q13
▶ OPEN SIMULATORGlycogen branching enzyme GBE1
α-1,4-glucan segment → α-1,6 branch
Retaining GH13 on 5CLW. Deposited maltoheptaose sits far from Asp357 — surface sugar, not the catalytic occupancy. Donor and acceptor are schematic.
EC 2.4.1.18 · PDB 5CLW
▶ OPEN SIMULATORLiver glycogen phosphorylase PYGL
glycogen(n) + Pi → glycogen(n−1) + α-D-G1P
Phosphorolysis on 1FA9. Crystal GLC is an inhibitor analog, not glycogen. Catalytic Pi is not deposited. PLP phosphate is the acid/base; AMP is allosteric.
EC 2.4.1.1 · PDB 1FA9
▶ OPEN SIMULATORGlycogen debranching enzyme AGL
4-α-transferase | amylo-1,6-glucosidase
One apo EM mesh, two tabs: 8ZEQ. Tab 1 transfers the stub (Asp526). Tab 2 hydrolyzes the leftover α-1,6 glucose. Not two genes.
EC 2.4.1.25 · 3.2.1.33 · PDB 8ZEQ
▶ OPEN SIMULATOR