Plant Physiology - Lecture Notes - O. M. Tarnopilska 2019

5. Plant Respiration
5.6 Direct Sugar Oxidation

Some Bacteria, Fungi, and marine Algae are capable of oxidizing unphosphorylated glucose. Initially, α-glucose is converted into the β-form with the participation of mutarotase.

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Figure 5.4 - Pentose Phosphate Pathway: 1 - glucose-6-phosphate dehydrogenase, 2 - gluconolactonase, 3 - phosphogluconate dehydrogenase (decarboxylating), 4 - phosphopentose epimerase, 5 - phosphopentose isomerase, 6 - transketolase, 7 - transaldolase, 8 - transketolase,

9 - Triosephosphate isomerase, 10 - aldolase, 11 - phosphatase,

12 - hexosephosphate isomerase (according to V. V. Polovyi)

Then, flavin-dependent glucose oxidase removes two hydrogen atoms from the CHOH group of a glucose carbon atom and transfers them to molecular oxygen, producing hydrogen peroxide. It is decomposed by catalase and peroxidase. In the process, glucose is converted into gluconic acid lactone, which undergoes non-enzymatic Hydration to form gluconic acid. Following phosphorylation, gluconic acid breaks down into pyruvic acid and 3-phosphoglyceraldehyde.



Last update: 07/08/2026

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