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PW-035 Carbohydrate Metabolism Catabolic (minor) unreviewed

Sorbitol / Polyol Pathway

Glucose Fructose (via sorbitol)
Compartment
Cytosol
Main tissue
Lens, retina, kidney, Schwann cells, seminal vesicle
Rate-limiting
Aldose reductase (AKR1B1)
Steps
2

Reaction steps

In source order, 2 total

showing 1–2
  1. 1

    Glucose + NADPH + H+ -> sorbitol + NADP+

    Aldose reductase (AKR1B1) 1.1.1.21 ST-0299 Irreversible/directional rate-limiting NADPH
    In Glucose NADPH H+
    Out Sorbitol NADP+
    › Notes

    Rate-limiting. High Km for glucose, so flux rises sharply in hyperglycaemia. Also reduces galactose to galactitol.

  2. 2

    Sorbitol + NAD+ -> fructose + NADH + H+

    Sorbitol dehydrogenase (SORD) 1.1.1.14 ST-0300 Reversible NAD+
    In Sorbitol NAD+
    Out Fructose NADH H+
    › Notes

    Absent or low in lens, retina, kidney and Schwann cells, so sorbitol is trapped there; osmotic damage underlies diabetic cataract, retinopathy and neuropathy. Seminal vesicles use this route to make fructose for sperm.

Showing all 2 steps.

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