Food Chemistry and Fish in Nutrition

6.4.1.5. Conversion of propionate into succinylCoA

Propionate resulting from fatty acid matabolism enters the main gluconeogenic pathway via the citric acid cycle after conversion to succinyl-CoA. Propionate is first activated with ATP and CoA by an appropriate acyl-CoA synthetase.

Propionyl-CoA synthetase

Propionate + ATP + CoA → Propionyl CoA

Propionyl CoA formed undergoes a CO2 fixation reaction to form D-methylmalonyl-CoA, catalyzed by propionyl-CoA carboxylase. This reaction forms a malonyl derivative and requires the vitamin biotin as a coenzyme.

Propionyl-CoA carboxylase

Propionyl CoA + CO ₂ + H₂O → D-methylmalonyl-CoA

D-Methylmalonyl-CoA must be converted to its steroisomer, L- methylmalonyl-CoA, by methylmalonyl-coA racemase before its final isomerization to succinyl-CoA by the enzyme methlmalonyl-CoA isomerase.

Methylmalonyl-CoA racemase

D-Methylmalonyl-CoA ↔ L- methylmalonyl-CoA

M ethylmalonyl-CoA isomerase

L- methylmalonyl-CoA ↔ Succinyl-CoA

It is converted into malate which is then converted into phosphoenol pyruvate and finally to glucose.

Succinyl-CoA → Malate → Phosphoenol pyruvate → Glucose

Thus glucose can be formed from fatty acids