Fig. 1.

Schematic of the glycerol metabolic pathway in E. coli. Protein members of the glycerol metabolic pathway includes glycerol facilitator (GlpF/AQP), a member of the aquaporin family of major intrinsic proteins. The soluble glycerol kinase (GK) phosphorylates glycerol to G3P. Another membrane protein constituent of this pathway is the transporter for the uptake of G3P (GlpT) with concomitant exit of Pi. Oxidation of G3P to DHAP is catalyzed by the monotopic membrane enzyme, glycerol-3-phosphate dehydrogenase (GlpD), a primary dehydrogenase. Concurrent with oxidation of G3P is reduction of flavin adenine dinucleotide (FAD) to FADH₂, which passes on electrons to ubiquinone (UQ) forming the reduced form (UQH₂) and ultimately shuttling electrons to oxygen or nitrate.